LP#1712637 Patron edit hold pickup location repairs

LP#1712637 Patron edit hold pickup location repairs

1. Allow setting the hold pickup location independant of the home
   library.

2. Disable org units in the pickup lib selector that are not viable hold
   pickup locations (can_have_vols=f)

3. Consistent w/ the XUL client, allow a patron to be created without
   selecting a default pickup location.

To test:

[1] Register a new patron and confirm pickup location is initialy unset.
[2] Confirm pickup lib options are viable pickup locations.
[3] Apply a pickup location different from the home library and confirm
    the home library selector remains unchanged.
[4] Confirm saving the patron applies the expected pickup location value.

Signed-off-by: Bill Erickson <berickxx@gmail.com>