#51 Refund handling

[Eric D. Nielsen]

As mroe competitions use the payment tracking tools; more
sophisticated needs are emerging.

One need is for the ability to handle/track refunds.

DCDI uncovered two types of refund needs:

1. A person paid more than they should have (typically via PayPal)
because the software wasn't offering the advertised early registration
discount

In this case, the payment is full "dispersed" and accounted for by its
line-items. Each line items is overpaid, and each person on that
payment is likely overpayed. A refund should be issued to the
orginal payer in the amount of the total over paid with breakouts to
the source line-items so that everything balances

2.A team paid for people who don't exist. The top level payment
node now has unallocated funds which will likely need to be
refunded, but its probably hard to add indidual line itmes.

Other issues:
Cancellation refund policies are sometimes tiered (100% before
XXX, 50% after YYY, 0% after ZZZ)