Teach marc_export how to export bibs for specified libraries

Teach marc_export how to export bibs for specified libraries

Useful shortcut for getting the bibs for libraries based on the
non-deleted callnumbers they have attached to non-deleted bibs.
Doesn't guarantee that they also have either a visible copy or
localized URI attached but whaddya want, magic? :)

Usage: marc_export --library BR1 --library BR2

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
git-svn-id: svn://svn.open-ils.org/ILS/branches/rel_2_1@20240 dcc99617-32d9-48b4-a31d-7c20da2025e4