Bug 643: Allow override of 'debarred' status

Bug 643: Allow override of 'debarred' status

Add a button to temporarily override patron debarment.

To test:
1) Go to patron check out page
2) If patron has been debarred (eg. due to having fees),
   there is no way to check out to that patron.
3) Apply patch
4) A debarred patron check out page now has a button for
   "Override debarment temporarily" - clicking on it
   should allow checking out to that patron.

Signed-off-by: Aleisha <aleishaamohia@hotmail.com>

Rebased because patch did not apply

Signed-off-by: Aleisha <aleishaamohia@hotmail.com>
Signed-off-by: Nick Clemens <nick@quecheelibrary.org>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Tested with/without force_checkout and superlibrarian permission.
Also checked crafting a URL is no longer working.
No regressions found.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>