Enhanced the Biome Dictionary

This has the same premises as https://github.com/MinecraftForge/MinecraftForge/pull/1193 however it is far more flexible in defining biomes that would otherwise need their own new types.

Vanilla biomes have all been updated to make use of the new types. DESERT and FROZEN have also been renamed to SANDY and SNOWY to be more specific and better describe when they should be used. DESERT and FROZEN still remain however, but are remapped accordingly.