Integrate terrain generator

[Bezude]

Terrain is still made from an old bitmap. The terrain generator needs to be hooked into the rest of the game. Issues that will arise directly as a consequence of this integration include:

• Save/Load of terrain so it's not generated every time.
• Establish a scale/unit system to know how 1 unit of terrain space relates to 1 unit of fooman space.
• Data chunking system. There's a lot of terrain and we don't want to run all of it through the render pipeline every frame.

[drewmalin]

Chunks of terrain should know what type (or set of types) they are, for example: 'DESERT,' 'PLAINS,' 'TUNDRA,' etc. Terrain type should be used to select entities from the library.xml file and place them appropriately depending on the 'commonness' of the entity (also stored in the library.xml file).