Lots of style changes

Style changes for Renderable.hpp/cpp

Also a change in Renderable::UpdateBufferGroups.
Now during VAO setup the shader attribute location is queried
from the material's shader.

Style changes for Material.hpp/cpp

Also Material::ActivateTexture now takes a GLuint  instead of
TEXTURE_TARGET. The target is just a offset of GL_TEXTURE0
so the target parameter is just added to GL_TEXTURE0.

Style changes for Graphics.hpp/cpp

Also changed GL::RemoveRenderable to use the list's remove method.

Style changes for Mesh.hpp/cpp and MD5Mesh.hpp/cpp

Style changes to Shader.hpp/cpp

These changes weren't to heavy as the class will
be undergoing heavy rework a bit later.