Added a web page front end to view the maze.
Fixed non-moving cell problem; I was trying to set a reference to a pointer when
what I really wanted was a pointer to the pointer, which isn't possible in js.
Had to resort to <barfs> a global var.

Maze is now playable and solvable.  Left to do is
- make it pretty
- provide 'hint' mode where the diversions are removed.