Bug 25826: Add a warning to the about page

Bug 25826: Add a warning to the about page

This patch adds a warning to the about page if the biblionumber field is
hidden at the OPAC or staff interface.

Test plan:
Hide the biblionumber to some framework
Confirm that there is a warning on the about page

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
(cherry picked from commit 6b8748248b6ef27783a222bbed83da9e5207fd7a)
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>