LP#1916403 Staff catalog search form labels

LP#1916403 Staff catalog search form labels

Provides label tags for staff catalog search form fields.

Most labels in the form are visible. I have used the sr-only class to
make labels available to screen reader users while hiding them from
sight on the publication date range fields, which I think are easy
enough to use without visible labels. However, this combination of year
and operator dropdowns is not well organized for screen reader users,
and we should rethink the order and wording of these fields.

To test, visit staff/catalog/search and inspect each form field. Verify
that each one has a <label> tag where the for attribute matches the ID
of the associated form element. (Checkboxes wrapped in the <label> tag
still need matching ID and for attributes for consistent ARIA support.)

Signed-off-by: Stephanie Leary <stephanie.leary@equinoxOLI.org>
fix

Signed-off-by: Stephanie Leary <stephanie.leary@equinoxOLI.org>