Move subdivs into arrays for O(1) access
Done: Make data load on demand
Done: Load objects into arrays instead of lists
Done: Order polygons
Done: Parse TDB
Done: Parse MPS
Done: Parse NET - unknown bytes at the end of some roads
Parse unknown data in RGN/TRE, needed for routing.
Parse NOD
Parse TYP
Parse MDR
Parse SRT
Parse DEM
Parse TRF