Add option to Tilemap to disable graphics caching about flashpunk

[noonat]

I expect this would be a big performance win for mobile GPU rendering, too, where texture switching tends to be costly.

[whitingjp]

Are there proven situations where rendering a Tilemap tile-by-tile is prohibitively slow? To my mind the caching functionality is uneccesary bloat; more memory usage, less flexible, poor performance/difficulties optimising for large tile maps. I'm happy to be proven wrong though.

Could we get away with dropping the caching functionality altogether? If there are rare cases where where caching is necessary it would be pretty trivial to achieve this in game code.