Bug 25471: Add DataTables to MARC subfield structure admin page

Bug 25471: Add DataTables to MARC subfield structure admin page

This patch adds DataTables sorting and filtering to the table of
subfields shown on the MARC subfield structure administration page.

To test, apply the patch and go to Administration -> MARC bibliographic
framework.

 - From the 'Actions' menu, select 'MARC structure.'
 - From the 'Actions' menu, select the 'View subfields' link for a tag
   with multiple subfields.
 - On the page showing all the subfields for the tag, confirm that the
   table is sorted by default by subfield and that sorting works
   correctly.
 - Confirm that the search form at the top of the table works.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>