Gloo clean parser

Do not merge !

I take your gloo clean and separate GLSL parsing from Shader classes. I think this will ease the task of integrating GLSL > 1.20. Also, it can used to extract more stuff (just run parser.py and look at included source files).

I may have messed up with latest push, so I ended up with more modifications that I thought. Important files are parser.py and shader.py.