Map 3d conversion WIP

What seems to work:
- Loading all map layers at once on game start
- Shifting all map layers at once when moving around

What doesn't work:
~~- There seems to be a strange offset of things on the lower z-levels. It's actually pretty hilarious, you can only drop down into the basement, and have to move back to the stairs which will spawn you into the wall of the evac shelter.~~
- Saving doesn't work, still need to track this bugger down. =(
A note here, if this is invoked on a tinymap (which it pretty much always should be), my_MAPSIZE is going to be 2, so it *is* only going to be generating as many submaps as are needed.
Leaving the delete grid[... at the end is a bit of paranoia.