Bug 20472: Edit URL field on staff form

Bug 20472: Edit URL field on staff form

This patch makes the following changes:

Add menu option Edit URLs.
Edit modal form to edit URLs.
Save URLs via ajax call to svc/article_request (Add action update_urls).
Add URL column to pending and processing table.
Allow Edit URLs for pending table too (just as Complete).
Do not allow 'Complete request' if a scan request has no URL(s).

Test plan:
[1] Add a few scan and photocopy requests.
[2] Fill url-A and url-B in two separate scan requests.
[3] Verify that these two urls are really saved (refresh form).
[4] Check that you cannot complete a scan request without URL and that you
    cannot add a URL to a photocopy request.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>