Bug 37242: Don't use the term branch in cash register administration

Bug 37242: Don't use the term branch in cash register administration

This patch replaces the word "branch" with "library" in the cash
register administration template in order to make it consistent with our
terminology guidelines.

To test you must have UseCashRegisters enabled.

- Apply the patch and go to Administration -> Cash registers.
- Confirm that the "Filter by" control at the top of the table reads
  "Filter by library."

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>