Bug 22198: Add granular permission setting for Mana KB

Bug 22198: Add granular permission setting for Mana KB

This patch adds a separate permission for managing Mana KB.

To test, apply the patch and update the database.

 - Open the permissions page for a patron with staff client privileges
   - Confirm that there is a "Manage Mana KB content sharing
     (manage_mana)" permission.
   - Leaving this new permission unchecked, log into the staff client
     with as that patron and go to the Administration home page.
       - The "Using Mana-KB" link should not appear.
       - Navigate directly to /cgi-bin/koha/admin/share_content.pl. You
         should get a "permission denied" message.
   - Modify the patron's permissions to grant them access to Mana KB.
       - Confirm that the link now appears on the Administration home
         page and that the user can access the page.

Signed-off-by: Maryse Simard <maryse.simard@inlibro.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>