LP#1701001: add search-to-hold to catalog app

LP#1701001: add search-to-hold to catalog app

This patch teaches the web staff client's catalog app how
to activate the patron search button in the embedded catalog's
place hold form. It also adds a handler for the button action
to display a modal to allow the staff member to search
for and select a patron, then injects the patron's barcode
into the form.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Chris Sharp <csharp@georgialibraries.org>
Signed-off-by: Jason Etheridge <jason@EquinoxInitiative.org>