Bug 31615: Allow checkin of items bundles without verifying their contents

Bug 31615: Allow checkin of items bundles without verifying their contents

This patch adds a button in the "bundle verification" modal to skip
this step and do the checkin anyway.

Test plan:
1. Create an items bundle (see bug 28854 comment 458)
2. Check out this bundle, then return it. The "bundle verification"
   modal should appear
3. Leave the textarea empty and click on "Confirm checkin without
   verifying bundle contents"
4. Confirm that the bundle was correctly returned, and no items were
   marked as lost

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>