Initial commit
Initial implementation of the Beagle compiler

Include the basic AST classes and some useful utility classes.
The Beagle grammar include the initial language features:
'if', 'while', 'do while', 'break', 'continue',
'return', 'switch', 'synchronized', 'try', 'throw', enum declaration,
annotations use and declaration, constructors and expressions.
Included license information.
Add missing AST files
Implements class, field and method conversion to procedure form (AST -> PST)
First attempt to generate C code from Beagle