Bug 13547: Add item field 3 (Materials specified) to the OPAC holdings table

Bug 13547: Add item field 3 (Materials specified) to the OPAC holdings table

Test plan:

1- View a record with Materials specified (field 3) data in the opac
2- Apply patch
3- Log in to staff client
4- Home->Administration->Column Settings->OPAC->holdingst
5- Set item_materials visibility
6- Refresh OPAC page
7- Confirm that the materials specified column has been added after the
   Call number column.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>