Small logic change.s
Add Box2d world.
Player moves by applying forces to its physics body.
Wall not currently working.
Walls now functioning correctly.
Changed to CSV from compresed file format due to compatibility issues with GWT.
Bullet is now a box2d object.
Box2d objects are now scaled correctly.  32px = 1 metre.
Added collision filtering.  Bullets from player will not collide with player.
Removed bitMask from walls.  They should collide with all objects.
Added MyContactListener class
Added MyContactListener class
Bullet bodies are destroyed when colliding with wall.