Move from legacy OpenGL 2.1 to modern OpenGL 4

[dgavedissian]

• [x] Replace all calls to glBegin / glEnd with a helper type that generates VBO's and calls glDrawElements automatically.
• [x] Add a debug check in all locations of glDraw*, to see where we aren't using shaders.
• [x] Implement a shader for all places we aren't using a shader so far (and thus relying on the fixed function pipeline).
• [x] Once fixed function pipeline features are removed, port GLMatrix.
• [x] Remove deprecated features (like point / line smoothness (?)).
• [x] Port shaders from GLSL 1.x to GLSL 3.3
• [x] Enable Core profile.