Chieftain Loot improvements

So the first attempt at Chieftain loot didn't really work out. Instead
of having Chieftains drop arrows in normal loot, I've changed it so that
Chieftains have a separate check to drop 30-50 arrows with every kill.
This makes sense, because Chieftains have arrows themselves to fire.

This way players can build fire/archery without chieftains' loot profile
being wasted on arrows.