Potential alpha surface culling issue fix.
Got rid of separate chains for water and alpha surfaces.
Use sky box shader to draw Quake 2 sky.
Separated non-map Quake BSP models as separate model type and separated it's data.
Removed loading of lumps that non-map BSP models don't use.
Common loading methods for Quake BSP models.
Added Quake BSP load helper class.
Free up BSP29 memory that doesn't need to be preserved after loading.
Moved foliage surface data.
Moved grid surface fields.