Routing and GridMaze working together

Changed GridMap so it didn't crash everything (see the cpp diff!  Had a
hard time noticing it.)
Made GridMap inherit from Maze, included MazeImports.h which represents
what the Router needs (should rename).
Made example routing code in Working and deleted other test code.
Made Routing compatible with GridMap.
Fixed the "final" bug in Routing (should work "perfectly" now) - the
router finished when it found the goal whereas it should continue until
there are no cheaper paths available.  Ie, it wasn't doing A* properly.
That's basically all the changes in .cpp and .h.