Bug 23436: add a label for duplicate backend

Bug 23436: add a label for duplicate backend

Reproduce issue:
 - Enable "EnableAdvancedCatalogingEditor" preference
 - Go to cataloguing and click on advanced editor
 - Click on the down arrow in "Save to catalog" menu
 - You should see an undefined named save backend

Test patch:
 - Enable "EnableAdvancedCatalogingEditor" preference
 - Go to cataloguing and click on advanced editor to save preference to
   the cookie
 - Click on the down arrow in "Save to catalog" menu
 - You should see a "Duplicate" named backend

Test Bug 16232 for no regression:
 - Search for a biblio in catalog
 - Click in "Edit record"
 - Advanced editor should appear.
   SUCCESS => browser url ends with #duplicate/{original biblionumber}
           => Title above toolbar is "Editing duplicate record of
              #{original biblionumber}"
 - Save
   SUCCESS => browser url ends with #catalog/{new biblionumber}
           => Title above toolbar is "Editing catalog record #{new
biblionumber}"

More test:
 - Search for a biblio in catalog
 - Click on "Edit record"
 - Advanced editor should appear
 - Click on the down arrow in "Save to catalog" menu and click on
   Duplicate,
 - Record should be saved as a new one (same behavior)

Signed-off-by: cori <corilynn.arnold@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit a8ddf55667f60a3cdc23ef0b6272921bc975bc73)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>