Added Warp tiles, multiple maps

all maps are loaded in from the world.txt file. Warp tiles require more fields than regular tiles, in this format:

character
type [2 is a warp tile]
[id of warp map, indexed by 0 as the order they appear in world.txt]
[start position on that map after warp X]
[start position on that map after warp Y]
descriptoin