Add pom.xml to build the code generation portion of the Python 3 target against declared ANTLR reference dependencies
Add ErrorQueue.java since the "test" artifact from the ANTLR Tool is not published in Maven Central as of release 4.3
Implement Target.getVersion by referencing RuntimeMetaData.VERSION since the compilation environment is now strictly controlled
Include complete V4 Tool content in shaded jar file
Fix Javadoc comments which produce build errors under Java 8