Modernise mesh rendering routines

[optimus-code]

Goal - To use Vertex and Index buffers for all mesh rendering routines

Issues

• Quake builds up geometry every frame combining static + dynamic lighting
• The current data structures are not suitable for creating VBOs and IBOs, we need to generate indices and potentially reformat mesh data
• For "Alias Models" (any non-sprite, non-BSP surface mesh) each frame has vertex data that would need to be combined and indexed.
• Lightmap data is calculated on the fly which isn't really conducive to the modern approach with shaders, preparing things ahead of time.

Tasks

• Refactor entity mesh routines and convert to OO based approach, to support eager generation of VBOs and go away from intermediate mode mesh generation.
• Determine the implications of switching approaches, how does it effect PVS, occlusion etc. Systems may need un-'spaghettifying'.