Bug 16485: collection column in Item search is always empty

Bug 16485: collection column in Item search is always empty

This patch fills the column 'Collection' in item search from the item values.

To test:
- Go to item search
- Reproduce issue from initial comment
- Apply patch
- Verify that the column 'Collection' is filled

Still to do, but outside of my datatable skills:
Filter by drop down in the column header does a substring search.
Example: Filter for 'Fiction" returns both 'Fiction' and 'Non-fiction' items.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Laurence Rault <laurence.rault@biblibre.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>