EngineBackend renamed to IEngineBackend
Added window system related method to the IEngineBackend interface
Exceptions derive from std::exception / CompilationError exception implemented
Added the getMaterial method to the IModel interface
Added the setNamedUniformMat4 method to the IMaterial interface
Implemented the initial attribute bindings in gl_Program (POISTION, NORMAL)
glShader: checkCompilation is now a method + on error throws a CompilationError exception
Removed opengl/main.cpp
gl/Material class only pushes a uniform if it is available in the shader (implemented setNamedUniformMat4)
gl/Model class handles attributes now.
Removed most of the testing code in gl/Renderer
gl/Shader properly handles the possibily of errors in reloadFile
Added UniformMat4 to gl/Uniform.h
Added gl/EngineBackend initial implementation of the IEngineBackend interface