Develop Java Source Translator

[DavePearce]

In addition to a transformation from WyIL bytecodes to Java bytecodes, it would be useful to have a translation to Java source. This would help on a number of fronts, including:

1. Ease of Integration with Existing Code Bases. In some cases, people may prefer to generate Java source code as this can exist independently of Whiley, and can be updated manually if necessary.
2. Ease Understanding of Mapping between Whiley and Java. Developers may look at the Java source produced from a given Whiley file to help them understand the mapping. This would be useful even if their build actually goes straight to JVM bytecode.
3. Ease Development of Java Backend. Debugging Java source code is much easier than Java bytecode. As such, looking at the generated Java source will be much easier than at the bytecode. Furthermore, it's easier and quicker to play around with ideas at this level, since bytecode is very finickity.

There are some issues here, of course. We need to ensure the relationship between the Java source produced and the Java bytecode produced is (ideally) identical. Furthermore, in generating Java source, it would be very nice to pull comments over from Whiley source files into the generated Java source files and/or generate Javadoc.