Added seeded-random Biomes to the Terrain Generator
This is rough, but it actually looks much better than I expected already!
Optimized previously unused terrain.BiomeGenerator and made it use SimplexNoise
Removed references to the odd BIOME_BLOCK_COUNT system
Removed a few unused globals to do with old biome systems
Cleaned up terrain.generate_sector, but its still quite messy
Terrain Generation: Fixed one cause of empty sectors