* Implemented some new classes to make code tidier (mesh class, terrain manager).

* Fixed normal generation for marching cubes terrain, texturing should be less buggy now.

* Added a bunch of comments around the place for my own sake so I can remember what I'm doing.

* Added more musings to the TODO list...

* Made voxel field generation in MCTerrainClass slightly more efficient (got rid of the density3DArray stuff).