Very basic HP and damage for both player and enemies.  Enemies damage the player on collision and projectiles damage enemies.  Player and enemies stop updating when dead, but are not destroyed yet.  Also adds two enemies to level 1.

Also adding debug_say method to GameObject.  All game objects have a debugName, defaulted to "unnamed object".  debug_say takes in any string and will print the object name followed by the message.  Convenient for debugging or status messages.