* add ancient beats monster to rpg.atlas
* many thanks to http://ancientbeast.com/
* add methods to SktGameInterface
- (id) addRandomRobotAt: (CGPoint) location
- (id) addRandomRockAt: (CGPoint)  location;
- (id) addRandomBonusAt: (CGPoint)  location;
- (id) didBeginContact: (SKPhysicsContact *) contact;
* add method setupLevel to SktGameRpg
* monster and rocks are built at game start