1. Changed DungeonSchematic to use an external instance of Random rather
than initializing its own.
2. Created the Pair class, a strongly-typed tuple that was needed in
PocketBuilder.
3. Added a missing calculation in NewDimData for setting the packDepth
field during dungeon initialization.
4. Finished code missing in PocketBuilder. Changes listed above were
needed for this.
Replaced several core classes from DD with new classes to enforce
integrity checks. Rewriting everything that depended on those classes is
a massive undertaking but it should simplify our code and prevent the
many bugs we've seen lately. The rewrite isn't done yet, just committing
my progress so far.
