Refactor the fix for duplicate pachinko transfers

 - Add a for_payday parameter to get_current_takes, on the pattern of
   Participant.get_tips_and_total. I believe this adequately reproduces
   the semantics of the inline takes query currently on the fix-payday
   branch.

 - Teach genparticipants about the different loops, harmonizing the
   semantics of that generator in the various loop cases. Now it knits
   in different extra info based on the loop: tips and total for
   payin/payout, takes for pachinko.

My goal here is to provide a consistent implementation of the several
payday loops.