* Sampler have getters for all parameters
* Texture gets a base class
* TextureBuffer moved to own file

Texture is still compatible with the old Texture class, new classes will be based on TextureBase and Texture will only remain for compatibility!

This loader gets the OpenGL function pointers and checks for extensions. It is an alternative to GLEW and has the advantage that it works out of the box on MacOS with a core profile and also allows only to include the defines and function declarations of a specific OpenGL version. This way the usage of 'wrong' functions can get caught during compile time (e.g. when developing for 3.2 on a machine that supports GL 4+). GLEW can still be used if desired!
The loader code is based on a modified output of glLoadGen (1.0.3), a bunch of LUA scripts that create the loader code. It's not a ready to use external library so the resulting code gets embedded directly into ACGL.