Add support for "pom" dependency types

Starting job of type [installplan] with identifier [extension/plan/org.renjin:renjin-script-engine/wiki:xwiki]
Resolving extension [org.renjin:renjin-script-engine/0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-appl-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:gcc-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-blas-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:gcc-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-math-common-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:gcc-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-nmath-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:gcc-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-blas-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-math-common-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-lapack-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:gcc-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-math-common-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-blas-0.9.2719] on namespace [Home]
Resolving extension dependency [org.apache.commons:commons-math-2.2] on namespace [Home]
Resolving extension dependency [org.renjin:gcc-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [com.github.fommil.netlib:core-1.1.2] on namespace [Home]
Resolving extension dependency [net.sourceforge.f2j:arpack_combined_all-0.1] on namespace [Home]
Resolving extension dependency [org.apache.commons:commons-vfs2-2.0] on namespace [Home]
Resolving extension dependency [commons-logging:commons-logging-1.1.1] on namespace [Home]
Resolving extension dependency [ant:ant-1.6.2] on namespace [Home]
Resolving extension dependency [xerces:xerces-impl-2.6.2] on namespace [Home]
Failed to install optional dependency [xerces:xerces-impl-2.6.2] with error: ExtensionNotFoundException: Could not find extension dependency [xerces:xerces-impl-2.6.2]
Resolving extension dependency [xml-apis:xml-apis-2.6.2] on namespace [Home]
Failed to install optional dependency [xml-apis:xml-apis-2.6.2] with error: InstallException: Dependency [xml-apis:xml-apis-2.6.2] is not compatible with core extension feature [xml-apis:xml-apis/1.4.01] ([xml-apis:xml-apis/1.4.01])
Resolving extension dependency [commons-net:commons-net-2.2] on namespace [Home]
Resolving extension dependency [commons-collections:commons-collections-3.1] on namespace [Home]
Resolving extension dependency [HttpClient 3.1] on namespace [Home]
Resolving extension dependency [org.apache.jackrabbit:jackrabbit-webdav-1.5.2] on namespace [Home]
Resolving extension dependency [org.apache.jackrabbit:jackrabbit-jcr-commons-1.5.2] on namespace [Home]
Resolving extension dependency [org.slf4j:slf4j-api-1.5.3] on namespace [Home]
Resolving extension dependency [HttpClient 3.1] on namespace [Home]
Resolving extension dependency [com.jcraft:jsch-0.1.42] on namespace [Home]
Resolving extension dependency [com.jcraft:jzlib-1.0.7] on namespace [Home]
Resolving extension dependency [org.apache.maven.scm:maven-scm-api-1.4] on namespace [Home]
Resolving extension dependency [org.codehaus.plexus:plexus-utils-1.5.6] on namespace [Home]
Resolving extension dependency [org.apache.maven.scm:maven-scm-provider-svnexe-1.4] on namespace [Home]
Resolving extension dependency [org.apache.maven.scm:maven-scm-provider-svn-commons-1.4] on namespace [Home]
Resolving extension dependency [org.apache.maven.scm:maven-scm-api-1.4] on namespace [Home]
Resolving extension dependency [org.codehaus.plexus:plexus-utils-1.5.6] on namespace [Home]
Resolving extension dependency [regexp:regexp-1.3] on namespace [Home]
Resolving extension dependency [org.apache.maven.scm:maven-scm-api-1.4] on namespace [Home]
Resolving extension dependency [org.codehaus.plexus:plexus-utils-1.5.6] on namespace [Home]
Resolving extension dependency [Apache Commons Compress 1.18] on namespace [Home]
Resolving extension dependency [XZ for Java 1.8] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-asm-5.0.4b] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-guava-17.0b] on namespace [Home]
Resolving extension dependency [com.sun.codemodel:codemodel-2.6] on namespace [Home]
Resolving extension dependency [org.renjin:stats-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-nmath-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-appl-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-gnur-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-guava-17.0b] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:gcc-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-appl-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-blas-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:grDevices-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-gnur-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.jfree:jfreesvg-3.3] on namespace [Home]
Resolving extension dependency [org.renjin:graphics-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:grDevices-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:utils-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-gnur-runtime-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:utils-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:methods-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:stats-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:tools-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:datasets-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:renjin-core-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:utils-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:utils-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:grDevices-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:graphics-0.9.2719] on namespace [Home]
Resolving extension dependency [org.renjin:compiler-0.9.2719] on namespace [Home]
Resolving extension dependency [com.github.fommil.netlib:all-1.1.2] on namespace [Home]
Can't find descriptor for the component with type [interface org.xwiki.extension.handler.ExtensionHandler] and hint [pom]
class org.xwiki.extension.InstallException: Failed to resolve extension
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:776)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:309)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:277)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.start(AbstractInstallPlanJob.java:208)
    at org.xwiki.extension.job.internal.InstallPlanJob.runInternal(InstallPlanJob.java:88)
    at org.xwiki.job.AbstractJob.runInContext(AbstractJob.java:236)
    at org.xwiki.job.AbstractJob.run(AbstractJob.java:213)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: class org.xwiki.extension.InstallException: Failed to create an install plan for extension dependency [com.github.fommil.netlib:all-1.1.2]
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtensionDependency(AbstractInstallPlanJob.java:674)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installMandatoryExtensionDependency(AbstractInstallPlanJob.java:626)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtensionDependency(AbstractInstallPlanJob.java:510)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:993)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:773)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:309)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:277)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.start(AbstractInstallPlanJob.java:208)
    at org.xwiki.extension.job.internal.InstallPlanJob.runInternal(InstallPlanJob.java:88)
    at org.xwiki.job.AbstractJob.runInContext(AbstractJob.java:236)
    at org.xwiki.job.AbstractJob.run(AbstractJob.java:213)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: class org.xwiki.extension.InstallException: Unsupported type [pom]
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.checkTypeInstall(AbstractInstallPlanJob.java:846)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:927)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtensionDependency(AbstractInstallPlanJob.java:670)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installMandatoryExtensionDependency(AbstractInstallPlanJob.java:626)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtensionDependency(AbstractInstallPlanJob.java:510)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:993)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:773)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:309)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:277)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.start(AbstractInstallPlanJob.java:208)
    at org.xwiki.extension.job.internal.InstallPlanJob.runInternal(InstallPlanJob.java:88)
    at org.xwiki.job.AbstractJob.runInContext(AbstractJob.java:236)
    at org.xwiki.job.AbstractJob.run(AbstractJob.java:213)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: class org.xwiki.component.manager.ComponentLookupException: Can't find descriptor for the component with type [interface org.xwiki.extension.handler.ExtensionHandler] and hint [pom]
    at org.xwiki.component.embed.EmbeddableComponentManager.getInstance(EmbeddableComponentManager.java:212)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.checkTypeInstall(AbstractInstallPlanJob.java:844)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:927)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtensionDependency(AbstractInstallPlanJob.java:670)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installMandatoryExtensionDependency(AbstractInstallPlanJob.java:626)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtensionDependency(AbstractInstallPlanJob.java:510)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:993)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:773)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:309)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.installExtension(AbstractInstallPlanJob.java:277)
    at org.xwiki.extension.job.internal.AbstractInstallPlanJob.start(AbstractInstallPlanJob.java:208)
    at org.xwiki.extension.job.internal.InstallPlanJob.runInternal(InstallPlanJob.java:88)
    at org.xwiki.job.AbstractJob.runInContext(AbstractJob.java:236)
    at org.xwiki.job.AbstractJob.run(AbstractJob.java:213)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Finished job of type [installplan] with identifier [extension/plan/org.renjin:renjin-script-engine/wiki:xwiki]