Implemented //SetBiome.
Fixes #16
Merge pull request #19 from mc-server/SetBiome

Implemented //SetBiome.
Probably fixed reason why //extend didn't work properly.
@madmaxoft I think //expand now works the way you wanted.
Swapped //expand parameters.
It's now //expand [Blocks] [Direction].
If only //expand is used the amount of blocks is 1 and the direction is forward.
Merge remote-tracking branch 'origin/master' into PlayerState