Add encounter zones to every biome

[jakeHaasBlog]

need encounter zones so that we can start working on battle mechanics. just need simple placeholders because AI will eventually be generating the tiles

• [x] Encounter zones are added in each biome
• [x] Each encounter zone has its own ID
• [x] Each encounter zone ID is mapped to a list of a few creatures

[jakeHaasBlog]

Added some methods to BiomeGenerator (Base class of all individual biome generators) to make customizing each biome much easier

[jakeHaasBlog]

Added encounter areas to all bomes. Only customized a few biomes, the rest will have to be touched up later