Bug 27682: Add a floating table header for Search engine configuration

Bug 27682: Add a floating table header for Search engine configuration

This patch adds DataTables options to the tables on the search engine
configuration pages. The table on the "Search fields" tab will be
sortable, all tables will be searchable, and all tables will have
floating headers.

To test you should have the SearchEngine preference set to
"Elasticsearch."

- Apply the patch and go to Administration -> Search engine
  configuration (Elasticsearch)
- Test the tables under each tab, "Search fields," "Bibliographic
  records," and "Authorities," the table has a search filter and the
  header row "sticks" to the top of the browser window as you scroll
  down.
- The "Search fields" table should be sortable, but the other two should
  not--they have drag-and-drop row reordering.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>