Doors Work, Maps Save

Doors work and connect maps.  Connect maps match doors on the sides they
share.  Maps remember what you've seen when you come back.

Error --> The monsters/enemies should be updated by dungeon map, not by
the game state, so over time that causes enemies to become new walls,
with only one of them moving.  The enemy follows you across maps, but he
stays in the same place, while you end up on the other side of the map.

Made several classes Serializable.

Made some variables transient, because they load when the objects load.

Made it so that the normal render follows your character's position.
You can still use the mapX, mapY thing to do examine, just have to make
sure it is set up first, because it will not match at all once you
traverse maps.

Changed how OnScreenChar does images - it saves the ImageUtil string
name for the image, and then at render time, it will get the image from
ImageUtil.