Bug 21871: Show authority 856 links in the OPAC

Bug 21871: Show authority 856 links in the OPAC

This patch modifies the authority detail view in the OPAC so that any
links found in 856 tags are displayed and active.

To test, apply the patch and locate or create an authority record which
contains one or more URLs in 856 tags.
 - View this record in the OPAC and confirm that the links appear.
 - Test records with and without link text.
 - Test records with and without public notes.

Signed-off-by: Devinim <kohadevinim@devinim.com.tr>
Signed-off-by: Charles Farmer <charles.farmer@inLibro.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
https://bugs.koha-community.org/show_bug.cgi?id=21817

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>