Bug 19932: (follow-up) Add fixed footer to cataloging Z39.50 popup

Bug 19932: (follow-up) Add fixed footer to cataloging Z39.50 popup

This patch adds additional Bootstrap framework markup to the search form
so that the "Save" and "Cancel" controls are in a fixed footer at the
bottom of the window. This prevents the controls from disappearing down
off screen.

To test, apply the patch and go to Cataloging -> New from Z39.50/SRU.
In the popup window, both the search form and search results pages
should look correct.

Signed-off-by: Claire Gravely <claire.gravely@bsz-bw.de>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>