Investigate use of MMapFSDirectory

On the deployment check-list was a comment: For 1.8.10 only for MMAP, add "-Dorg.apache.lucene.FSDirectory.class=org.apache.lucene.store.MMapDirectory" to prod-app:/opt/SUNWappserver2/domains/domain1/config/domain.xml in the JVM command line.

This doesn't sound useless (as per the javadoc http://lucene.apache.org/java/2_9_1/api/core/org/apache/lucene/store/FSDirectory.html ). But it doesn't sound to be something we should do on the command-line, rather in the config or the plugin.

Currently, none-of-that is used in beta or prod.