Bug 25138: Terminology: Point of sale should use library instead of branch

Bug 25138: Terminology: Point of sale should use library instead of branch

This fixes the navigation on the Point of sale page:
Branch details => Library details

And the heading and the 'no register defined for this branch/library'
message on the page it links to.

To test:
- Activate cash registers and point of sales features
- Go to the point of sales page
- Verify text on the menu to the left
- Click on the Branch/library details - verify text and heading

Signed-off-by: Devinim <kohadevinim@devinim.com.tr>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>