Adjusted enemy behavior internally

-Added in a separate state for lowering (so we can make it smooth)
-Removed Enemy.SHOOTING, since it was slowly moving enemies out of sync
-Normalized Enemy.shootRange, renamed it to shoot_odds, and made it a class member
-Made Enemy.anim a class member
-Added enemy.update() to update the entire Enemy class easily
-Removed enemy.SAFE_SPOT, which was unused