Bug 23947: Phase out jquery.cookie.js: Authority merge

This patch updates the JavaScript which sets cookies during the
authority merge process so that it uses the new js-cookie library.

To test, apply the patch and perform a search in the authority module
which will return multiple results.

 - Select "Merge" from the Actions menu next to any result.
   - A message should appear at the top of the page: "Merging with
     authority: <title>".
   - Click "Cancel merge." The message should disappear.
 - Select a record to merge again.
   - Select another record.
   - The page should redirect to the authority merge page.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>