Some changes

- Update of two headers:
 - Core.hpp
 - Math.hpp

- Several changes:
 - Light Manager: I prefer iterators
 - OpenGL: The UV problem is solved, but you forget to change the cubemaps
 - Texture: GetSize() was returning a int instead of NzVector2ui
 - Algorithm: Simplification
 - Utility: Couldn't compile

- Add a file containing the writing style of the project, I don't know if it's a good or bad idea. Do as you want, this should be rewritten anyway.