Merge: Ballz improvements

Better concern division into modules, now works on Linux !
forces.nit module is not really used yet but will be.

PS : mnit_simple and mnit_ballz aren't launching on android at the moment, I'll fix this in a further PR

Edit: Fixed Android part

Pull-Request: #1587
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>