Upgrade to Maven Compiler plugin 3.2

Release Notes - Maven Compiler Plugin - Version 3.2

** Bug
    * [MCOMPILER-157] - Maven Compiler Plugin should add to compileSourceRoots for next plugins to consider as source directory for generated files 
    * [MCOMPILER-224] - Maven compiler plugin does not properly consume plexus compiler output

** Improvement
    * [MCOMPILER-159] - generatedSourcesDirectory should be included in list provided by org.apache.maven.project.MavenProject.getCompileClasspathElements()
    * [MCOMPILER-232] - Fix RAT Report

** Task
    * [MCOMPILER-220] - Fix o.a.m.p.c.CompilerMojoTestCase.testCompilerFork(), which fails when javac is not on the PATH