LP#1779743: add privilege expiration date to Group Member Details

LP#1779743: add privilege expiration date to Group Member Details

This patch adds the privilege expiration date to the list
of available columns in the AngularJS group member details
page. No equivalent change is needed to the experimental Angular
circ interface, as that column is already available there.

To test
-------
[1] Apply the patch.
[2] Navigate to a patron in the Evergreen staff interface
    and view the Group Member Details page.
[3] Verify that the privilege expiration date is now available
    in the column selector.

Release-note: Add privilege expiration date column to Group Member Details table

Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>
Signed-off-by: Jason Boyer <JBoyer@equinoxOLI.org>