Added teh Brian Code, Click to add walls, minor clean-up

--A* implemented by Brian
--Mouse button release callback function added to add or remove walls
--Changed "walls" to "initialWalls," it is only used for initialization
of map.cells now
--Made .draw check cell.occupied to draw instead of walls
--Deleted a lot of non-functional code
Revert "Added teh Brian Code, Click to add walls, minor clean-up"

This reverts commit e7dc944740c0682df0ceab277f956ce0e881aff9.
Merge remote-tracking branch 'origin/master'