Requests can now be placed "on hold", and getRequest() can ignore held
requests.
This required addition of a table, and another API call holdRequest().
Tests were not written here, which was a mistake. Unit tests and docs
are needed. A FIXME was added, at least.
Also, minor imporvements to reporting on fulfilled requests.
The idea behind this sort is to give monthlies top priority based on
their id number (i.e., when they hit $60, just get that shirt out to
them), and for annuals, make sure we prioritize based on how long it has
been since their last donation.
Analysis of IRS rules indicate that sometimes, a thank-you gift can't be
sent unless the percentage the gift is of the donation meets a certain
threshold.
This change allows the caller of this script to implement that sort of
threshold.
