Some reorganization and minor fixes to world I/O in preparation for big fixes.
Various world fixes:
- Changed createTileEntity to not take GlowBlock to save having to create one
  for every block loaded.
- Changed MultiBlockChangeMessage to not require conversion to an array.
- Changed tile entity loading to not create GlowBlock objects.
- Made RegionFile not flush on every chunk write.
- Changed getChunk() logic to not always create new GlowChunk objects.