Bug 24790: Add POS to the 'More' dropdown on the staff client

Bug 24790: Add POS to the 'More' dropdown on the staff client

This trivial patch adds 'Point of sale' to the dropdown.

To test:
1. Notice there is no 'Point of sale' entry in the staff dropdown
=> FAIL: No dropdown
2. Apply this patch and reload
=> SUCCESS: Point of sale displays and works
3. Play with enabling/disabling the feature and removing permissions
=> SUCCESS: The entry in the dropdown respects the configured
permissions and settings.
4. Sign off :-D

Signed-off-by: George Williams <george@nekls.org>
Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>