adds basics of projectile class and refactors some things from robot to
actor.
adds functionality for projectile actions and graphics
adds functionality so projectiles are correctly destroyed and not drawn.
adds method for robots to shoot projectiles
Merge branch 'master' of git@github.com:CSSDePaul/Computerized-Robot-Arena-Program.git
Refactors robot to provide a list of valid actions to the behavior
script.