Bug 17748: Show due date and availability in item search results

Bug 17748: Show due date and availability in item search results

This enhancement adds the availability of an item to the item search
results (i.e. shows if checked out or not). If checked out,
shows due date in item search results. The due
date column will also show when exporting results to a CSV file.

To test:
1) Apply patch and restart services
2) Set up two items. Check out Item A to a borrower. Leave Item B as
is not checked out, and not unavailable status.
3) Go to Search -> Item search. Scroll down and notice the Availability
radio options - Ignore, and Checked out.
4) Leave the Ignore option selected and do a search so that both items show.
5) Confirm the availability and due date columns are showing at the
right end of the table. Confirm Item A says Checked out and has a due
date. Confirm Item B says available.
6) Export all result to CSV. Confirm the results show in the CSV file as
expected.
7) Go to edit your search. Select the 'Checked out' radio option for
Availability and submit the search. Confirm only Item A shows in the
results (not Item B).

Sponsored-by: Bibliotheksservice-Zentrum Baden-Württemberg (BSZ)
Signed-off-by: Christian Stelzenmüller <christian.stelzenmueller@bsz-bw.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>