Remove test files
Add bullets and missiles

The player can now shoot bullets in a direction specified
by the mouse. A canon object can shoot bullets or missiles.
Missiles can change their flying direction to hit moving
targets, bullets can not.
Allow contact actions if player is not involved

Previously actions could only be created by a contact
if one of the fixtures was the player. Now any contact
can create actions. This allows bullets to be destroyed
if they connect with the level geometry or other objects
besides the player.