Added ImageHandler-class.
Made each projectile aware of which tank that fired it. Also added preliminary collision handling for projectiles.
World now has a size
Added MapBounds class
New worlds now adds a MapBounds automatically
Made the tank bounce when it hits the edge of the map.
Projectiles are removed if they hit the edge of the map.
Projectiles now destroy themselves
Removed old code for removing and destroying projectiles
Working on imghandler...
Reworked Play's update() and render().
Added different sprites for different projs.
Projectiles now remove themselves from their Tank's list of projectiles when they get destroyed
DefaultProjectile now has a shape of a rectangle
Merged Turret-Projectile > imghandler.
Added Shape, Size, Position to DefaultProjectile.
Changed the type of Map to ConcurrentHashMap

Fixes the ConcurrentModificationException when using turrets shooting
multiple projectiles at once.
* ConcurrentHashMap
Changed behavour of Projectiles collisions

Ignores collisions with other projectiles and the tank itself (owner).
This also fixes the bug with projectiles not reacting to collision with
MapBounds.
Proper merge, hopefully..