Renamed zone type of zone to terrain type of zone.

By renaming zone type of zones to terrain types, this avoids confusion.
There is a test and the ui seems to work.
Fixed backend confusion on zone vs terrain

As in, finished implementing terrain.
Front end now recognizes terrrain, not zone
Merge pull request #58 from lordnull/feature-mw-zone-type-rename

Renamed zone type of zone to terrain type of zone.