Bug 16268: Add confirm message for deleting circ and fines rules

Bug 16268: Add confirm message for deleting circ and fines rules

EDIT: Removes unnecessary code and uses confirm message in staff-global.js

To test:
1) Apply 16267
2) Go to Admin -> Circ and fines rules
3) Try clicking on Delete and Unset buttons
4) Confirm a confirm message pops up and works as expected

Sponsored-by: Catalyst IT
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>