Added loads of shit:

* Made changes to make mesh/renderable system more generic.

* Fleshed out terrainmanager with bunch of functions for creating and retrieving  chunks and their contents

* Added comments where they are needed, as usual. Fixed naming conventions and cleaned up code in marching cubes / procedural generation code.

* Added a bunch of links and ideas to TODO. As usual I haven't actually removed anything, because I dont do very much  useful work. :)

* Renamed some structs and functions in marching cubes class.