Allow renewCreep to target other players' creeps

[CBoon]

The idea of such a thing has spurred some awesome chat in the slack, like some renew-pit-stops for weary travelers, and it seems harmless enough to lift that target.my restriction (unlike recycleCreep ofc). More power to the players, right?

[CBoon]

Then again, remembered too late that renewCreep destroys a creep's boosts, so it's not so harmless a function after all... Still, a pity.