Bug 25428: Correctly encode link if authority subfield is a URL

Bug 25428: Correctly encode link if authority subfield is a URL

This patch modifies the script and template for showing the details of
an authority record so that if the authority subfield is configured to
be a link the link is correctly output in the template.

To test you must have an authority type configured with at least one
subfield designated as a URL:

 - Go to Administration -> Authority types
 - Select "MARC structure" from the actions menu for the authority type
   you want to modify.
 - Select "Subfields" from the actions menu for the tag containing
   the subfield you want to modify (for instance 856).
 - Edit the subfield you want to display as a link (e.g. subfield u).
 - In the subfield configuration form under "Advanced constraints" check
   the "Is a URL" checkbox and save your changes.

 - Apply the patch and go to Authorities in the staff interface.
 - Search for or create an authority record which contains URL
   information in the right subfield (for instance 856$u).
 - View the details for the record. Using the 856 example, the "8" tab
   should contain an active link pointing to the correct URL.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>