Bug 14790 - Add OPAC view link to items editor

Bug 14790 - Add OPAC view link to items editor

Test Plan:
1) Apply this patch
2) Find a record and open the items editor for it
3) Click the "Actions" button for an item
4) Choose the option "OPAC view"
5) A new browser tab should open to the OPAC details page for the record
   whose items you are editing.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>