Updated attributions
Added splash screen JPG
Added new splash screen class
Finished the simple projectile code
Added SVG to asset loader and added an error for an unrecognized asset
Added time delay between shots
Added common functionality from other classes
Removed game-specific actions
Cleaned up code, added splash image, added game states, added actions from
input engine, added new action for processing by input engine, added
ability to shoot, and added code to display score
Moved entity script include, and added splash screen and simple projectile
script include