Bug 11882: Add a new button to the checkout confirmation dialog when checking out...

Bug 11882: Add a new button to the checkout confirmation dialog when checking out a reserved item

This patch adds a "Don't Check Out and Print Slip" button to the dialog that appears
        when trying to checkout a reserved item.

Test case :
* Put a hold on an item for User A.
* Try to check out it item with User B.
* The "Please confirm checkout" box should appear. The "Don't Check Out and Print Slip" button should appear in this box.
* Click on the "Don't Check Out and Print Slip" button.
* A print popup will appear

Signed-off-by: Nick <Nick@quechelibrary.org>
Followed test plan, works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>