Bug 25936: Add option to send password change notices

Bug 25936: Add option to send password change notices

This patch add a new security notice to allow sending notification of
password changes to patrons. If enabled, the 'PASSCHANGE' notice will be
sent to respective patrons whenever their password is updated.

Test plan
1) Run the database updates
2) Enable the new feature by setting 'NotifyPasswordChange' to 'Notify'
3) Change a users password
4) Check that the notice appears in the patrons notices

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>