Move print statements out of resolve_fight so that AIs can call it witho...

...ut a bajillion lines of junk on human's screen.
I like the idea of moving the print statements out of resolve_fight. This string return value from resolve_fight doesn't seem right to me. Maybe just return the FightResult and then do the string formatting outside of the function call? The caller already has access to red_card and blue_card so that should be easy.