LP#1732761: Batch item edit and multiple values per field

LP#1732761: Batch item edit and multiple values per field

Previous to this commit, the display of multiple different values for a field
in the item attribute editor was simply to display no value.  Here we add a UI
component that presents the list of unique values, the number of selected
copies that use each value, and the ability to select just those copies using
a particular value by clicking on the desired value.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Kathy Lussier <klussier@masslnc.org>
Conflicts:
	Open-ILS/src/templates/staff/cat/volcopy/index.tt2
	Open-ILS/src/templates/staff/cat/volcopy/t_attr_edit.tt2