Bug 12478: Display facet terms ordered by number of occurrences

Bug 12478: Display facet terms ordered by number of occurrences

By default ES returns the facet terms ordered by most used, which makes
sense.

This patch removes resort done in the scripts (catalogue/search.pl and
opac/opac-search.pl) and moves it to the module.

For Zebra it's now done in C4::Search::getRecords, and there is no
change to expect (still alphabetically).

On the Elastic search side, we could imagine to let the library define
the order of the facets. The facet terms are now sorted by most used.

To test easily this change, turn on the displayFacetCount pref.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jesse Weaver <jweaver@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>