Added a command stack for the collisionHandler(last time), so that collided objects can add commands to the player.
Added isCollidedWithNonPlayer method to Collision Handler, for checking non-Player collisions. Incorporated into cantMove of Elevator
Had Elevator class check for collisions with the Player, and send him a LegalDisplace Command if so.
Now Terri is correctly displaced by the elevator, except sometimes there's an error...