Use numpy functions to load map FASTER!!!

(By two orders of magnitude?!)
Remove map caching.

Rather ugly hack made redundant by numpy stuff.
Remove dirtycache setting from config file.
Reorganise in-game image files.

Does this make sense?
Properly randomise cellarray['random'].
Reorganise terrain-type declaration.

Stuff in Map.py is a mess, will fix.
Remove older, non-overlapping sprites.

Look silly when rendered with the new ones.
Shuffle terrain loading about a bit.
Correct order of terrain.
Remove old locations of files.
Yet more issues with inadequately-deleted files.
Add neighbour-based directional sprite thingies.
Add demo neigbour-sensitive sprite for walls.
Merge pull request #33 from FLHerne/master

Create branch for adding new wall graphics