Fix Sketch -> Java translation

[droptablestar]

This broke with the switch to the new parser.

[chaserhkj]

I did a back-port of the old decoder (the module that does Sketch -> Java translation) to the new parser and AST data structure as a new command line flag, it is on master branch now. A section is also added to README to describe it.

It still lacks a lot of JSketch feature support, since they are not supported by the old decoder either. I'll continue to work on this to support the other JSketch features as many as possible. For now I will keep this issue open until a more complete set of JSketch features are supported by the decoder.