Bug 13417: Allow staff members to manage public lists

Bug 13417: Allow staff members to manage public lists

Currently a public list can only be deleted by its owner.
This means lists can exist infinitely.
This will introduce a new permission for list. With this permission, a
staff member will be allow to delete any public lists.

Test plan:
1/ Add the manage_shelves permission to a patron.
2/ Login with this patron
3/ Go on the public list view
4/ You should be able to edit all public lists

Followed test plan. Works as expected.
Signed-off-by: Marc Veron <veron@veron.ch>
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>