Modernize Renderer

[IllustrisJack]

No description provided.

[dgavedissian]

I just opened a PR to move us from legacy OpenGL 2.1 (with slow immediate mode APIs, some glitches in shaders) to modern OpenGL 3.3: #293

Next steps are:

• Remove Shader.SetFloat4 and related "global" Shader functions that depend on you having run shader:start first. Make those part of the shader itself i.e. shader:setFloat4.
• Add the concept of a "uniform buffer" which can be shared across shaders. Perhaps worth also supporting automatic uniform buffer population by parsing the GLSL shaders.
• Replace Draw.Clear/Draw.ClearDepth with the concept of a "render pass".
• Improve the Lua rendering API by getting rid of all the Push/Pop's everywhere around shaders. I want it to be solid and not depend on the "current" global state so much. Perhaps introduce a new "RenderState" type?
• Rename ShaderState to Material. Move render state features into Material? Need to think on this one.
• Incorporate ShaderVar.* functions into Shader i.e. ShaderVar.PushMatrix -> Shader.PushGlobalMatrix. Or perhaps, come up with a better abstraction for "global" variables (maybe uniform buffers?)