Added a workaround so that the dungeon list produced by
CommandAddDungeonRift does not have repeated names. Also cleaned up the
code a bit - it's a mess in there. Part of the rewrite eliminated the
bug that caused some dungeon names to be preceded by a backslash (or
slash). I've noticed a different bug now - the dungeon tutorial file is
being included in the list of dungeons. I'll be fixing that in the next
commit.
