Bug 16314: Show upload link for upload plugin in basic MARC editor

Bug 16314: Show upload link for upload plugin in basic MARC editor

This patch updates the basic MARC editor to provide a plugin name
variable to the template, allowing us to make a check on the name and
conditionally show an upload link if the "upload.pl" cataloging plugin
is selected.

To test, apply the patch and rebuild the staff client CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).

 - Go do Administration -> MARC bibliographic framework -> MARC
   structure -> 856 -> Edit subfields.
 - Edit the "u" subfield and select "upload.pl" as the plugin under
   "Other options."
 - Go to Cataloging and create or edit a MARC record.
 - Under tab 8 look for the 856 tag, subfield u. There should be an
   "Upload" link corresponding to the form field.
 - Click the upload link to confirm that it triggers a popup window with
   the upload form.
 - Confirm that other similar plugin links (for instance 100$a, 600$a)
   display the old "tag editor" icon.

Signed-off-by: Lisette Scheer <lisetteslatah@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit bdb64657f9c69387f264a333a7d040c9f1dba574)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>