Bug 30500: Allow patrons to change in transit holds pickup locations

Bug 30500: Allow patrons to change in transit holds pickup locations

This patch adds a way for patrons to change the pickup location for in
transit holds.

This is done in the OPAC on the holds table.

The feature is controlled by a new system preference:

* OPACInTransitHoldPickupLocationChange

To test:
1. Apply this patches
2. Run:
   $ updatedatabase
   $ restart_all
=> SUCCESS: system preference added
3. Have an in-transit hold for a known patron
4. Visit the holds table for the patron (OPAC)
=> SUCCESS: Hold in transit, cannot change pickup location
5. Enable the OPACInTransitHoldPickupLocationChange system preference
=> SUCCESS: Descriptive text makes sense and is idiomatic
6. Reload the OPAC page
=> SUCCESS: You can now choose a new pickup location
7. Choose one
=> SUCCESS: It works! Reloaded page pre-selects the new pickup location
8. Switch to the new pickup location library on the staff interface
9. Go to Circulation > Transfers to receive
=> SUCCESS: The hold is there!
10. Scan the hold
=> SUCCESS: Usual workflow follows
11. Sign off :-D

Sponsored-by: Montgomery County Public Libraries
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>