TileMap update performance

Discussion: http://www.html5gamedevs.com/topic/7409-tilemaps-changing/

It should remove the problem of updating stuff in a 100x100 tilemap making the engine recalculate every single update.(390 tiles changed in that map makes it a 100x100x390 loop.
Whould make the recalculate parameter in the setCollision functions unnecessary as well.