==== Duplicate Order Detection Improvements ====

Provides tools to make it more clear to staff when a purchase order or
items on an order have been ordered before.

===== Prevent Duplicate PO Names =====

Staff now have the option to specify a PO name during PO creation.
If the selected name is already in use by another PO at or below
the ordering agency for the PO, the user is warned, the save/submit
operations are disabled, and a link to the existing PO is display.  The
link opens the related PO in a new tab when clicked.

Selecting a name which is not yet used or clearing the name field
(which defaults upon creation to the PO ID) will clear the warning and
re-enable the submit/save operation.

Similarly, when editing a PO, if the user attempts to use a name already
used, the user will be warned and a link to the offending PO will be
displayed.

===== Show Existing Copies =====

In the select list and PO view interfaces, beside the lineitem ID #, we
now also display the number of catalog copies already owned at or below
the ordering agency for the bib record in question.

The count does not include copies linked to the lineitem in question
nor does it include copies that are in some form of lost, missing, or
discard status.