[Added] attack command for pets (currently only functional with an
attackable player as target)
[Added] pets can now attack any player that their owner can attack
[Added] pets can now be attacked by any player that their owner can be
attacked by
[Added] pets now turn red to any duel opponent of their owner

Change-Id: I9fe5f56ae0539de542f32addd5c2184ce5f9c7e3