Enable TPAC to display records via HSTORE-based unapi

Enable TPAC to display records via HSTORE-based unapi

Now that unapi requires HSTORE-based LIMIT and OFFSET arguments, take
the simplest possible approach to get get_records_and_facets() working
again.

In search results, we want to limit both the number of copies we get
back (defaulting to a maximum of 5 copies per call number) and the
number of call numbers we get back (defaulting to a maximum of 5 call
numbers), so that we don't get 50 call numbers each with 5 copies back
and wind up grinding Evergreen's performance down to a halt.

Rough thought is that the caller can filter through the (maximum) 25
hits that are returned to present their preferred results. For example,
a site could opt to show 5 different call numbers with just one copy per
call number, or 5 different copies for a single call number, or all 25.

Signed-off-by: Dan Scott <dan@coffeecode.net>