Bug 23321: Add cash register management

Bug 23321: Add cash register management

Add in administrative interfaces to allow the management of cash
registers.

Test plan:
1) Enable the use of cash registers by setting 'UseCashRegisters' to
   'Do'
2) Check that the 'Accounts > Manage cash registers' option now appears
   in the 'Administration' area.
3) Click through to 'Manage cash registers' and note the message
   suggesting you add your first register
4) Add you're first cash register
5) Note that the message has now been replaced by a table of cash
   registers including the one you have added in the previous step.
6) Edit the cash register created in step 4 and note that the table
   reflects the changes
7) Signoff

Sponsored-by: PTFS Europe
Sponsored-by: Cheshire Libraries Shared Services
Signed-off-by: Maryse Simard <maryse.simard@inlibro.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>