o Added initial save state mechanism, doesn't work currently.  Press F6
  to save, F7 to load, saves to game.save.

o More work on APU.

o Modified MappedMemory.AddMirrors to take uint32's so that UNMIRRORED
  can be passed in.

o Added initial MMC1 mapper support.  Swapping of PRG banks is currently
  wrong somehow, but almost there.