Add support for quick visit to already visited rooms

[stephenhaunts]

Once you have visited a room, you should be able to go straight to that room anytime, so if for example you are on one side of the map and you want to go back to the start room, you can just go straight to it with the goto command.

If you type goto on its own, it will list all the rooms you have visited.

This makes a game less frustrating for anyone that wants to move around the map quickly after discovering a room.