LP#1938835: release notes for the customizable staff portal

LP#1938835: release notes for the customizable staff portal

To test
-------
[1] Apply the patch.
[2] Verify that the Angular staff portal is now the default
    and that it displays the stock portal entries.
[3] In the new Staff Portal Page local administration interface,
    make changes to add, subtract, or modify portal page entries.
[4] Verify that those changes appear on the staff portal page and
    that they are sensitive to the workstation that the staff
    user is logged in as.

Sponsored-by: Pioneer Library System
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>