Make spine label settings configurable as org unit settings

Make spine label settings configurable as org unit settings

Note that due to the persist attribute on these XUL elements, a user
who has manually changed their spine label settings may not see the
org unit setting defaults for those particular settings if those
org unit settings are created or changed.

Now that the infrastructure is in place, We could make the org unit
settings take precedence over the persisted attributes if we think
that's the right way to go.

git-svn-id: svn://svn.open-ils.org/ILS/trunk@17341 dcc99617-32d9-48b4-a31d-7c20da2025e4