Made it so that the firing sequence checks for intersections with any
tank in the environment (other than the tank which fired the projectile,
although we might want to change this latter).

Firing sequence now works like this:
-Button is pressed, and handler in TankWars.java responds.
-The handler calls the turret.Fire() method which spawns the weapon
 currently selected into the environment.
-The weapon moves through the environment in the thread initalized
 in TankWars.java.
-If the weapon's bitmap intersects with the other tank then said
 tank has their tank.strikeTank() method called, this method references
 the weapon.directHit(). When explosions are implemented, struckTank()
 should have a boolean for determining if the tank was hit directly, or
 by an after effect (like an explosion).