Bug 26194: Add link to cash register management from message about missing registers

Bug 26194: Add link to cash register management from message about missing registers

In places where the interface warns the user about missing cash
registers we should provide users with permission a direct link to the
cash register management page.

To test, apply the patch and enable the UseCashRegisters and
EnablePointOfSale preferences.

If necessary, go to Administration -> Cash registers and remove any cash
registers for your library.

 - Log in to the staff interface as a user with "manage_cash_registers"
   permission.
 - Locate a patron who has outstanding fines.
 - Under Accounting -> Make a payment, click the "Pay" button next to a
   fine.
 - The page should show the message about missing cash registers with a
   button which take you directly to the "Add new cash register" form.
 - Perform the same check by selecting the checkbox next to a fine and
   clicking the "Pay amount" button and the "Pay selected" button.
 - Test the message shown at:
   - Tools -> Cashup registers.
   - Point of sale -> Register details
   - Point of sale -> Library details
 - Perform the same tests when logged in as a user without permission to
   manage cash registers. The messages shown in the previous steps
   should omit the button linking to cash register management.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>