Merge: Nitj: A compiler to Java code.

Merge: Nitj: A compiler to Java code.

Introduce a new compiler `nitj` that takes nit code and produce Java code.

Passes ~700/950 tests from the base*.nit test suite.

Since the commit serie is rather long, I suggest to read it comit by commit.

Some features still missing (maybe later):
* generics
* arrays
* varargs
* strings

Note: There is no concrete motivation beyond this engine. Did it for the lulz.

Pull-Request: #1577
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Jean-Philippe Caissy <jpcaissy@piji.ca>
Reviewed-by: Jean Privat <jean@pryen.org>