Replace hard-coded '(CONS)' for MARC control number identifier in authority records

Replace hard-coded '(CONS)' for MARC control number identifier in authority records

We created an actor.org_unit_setting, 'cat.marc_control_number_identifier', for
specifying the preferred MARC control number identifier, but when we create a
new authority record from the MARC editor, the hardcoded value of 'CONS' is being
used.

This teaches the staff client how to pull the appropriate value from the AOUS
when invoking the MARC Editor.

Resolves https://bugs.launchpad.net/evergreen/+bug/669245

git-svn-id: svn://svn.open-ils.org/ILS/trunk@18559 dcc99617-32d9-48b4-a31d-7c20da2025e4