Added a dimension

Finally did some work! Expect frequent commits now,  as I actually get
stuff done with my newfound time. Behold, from my test world:
[07:03:26] [Server thread/INFO]: Saving and pausing game...
[07:03:26] [Server thread/INFO]: Saving chunks for level
'Test'/Overworld
[07:03:26] [Server thread/INFO]: Saving chunks for level 'Test'/Nether
[07:03:26] [Server thread/INFO]: Saving chunks for level 'Test'/The End
[07:03:26] [Server thread/INFO]: Saving chunks for level 'Test'/Runic
Dimension
^^See that. That is the sound *ahem* log of progress!