More cleanups

Moved lumpnames enum into class.
Removed obsolete typedef.
Made getvector for entities more generic.
Beginnings of lightmap support.
More const'ing.
Attempt to move patches into normal vao, failed (in comments)
Replaced some 0s with nullptr
Changed some more casts to c++ style
Added loading for more lump types (not yet used)
Changed another loop to be range based