Import / export enhancements

Libraries using MFHD-based serials would like the ability to assign a default OU at import time, rather than having to manually edit all of the files after to change "\N" to the ID of the owning library.

1. We need to teach the exporter how to export the MFHD records that exist for a given bibliographic record.
2. We need to teach the exporter how to generate MFHD records that represent the holdings for a given bibliographic record.
3. We need to expose these options in the Vandelay interface.

Incoming bibliographic records have collection codes in the 852 (which subfield?); these need to be mapped to statistical categories.

When a new MFHD record is created, the 004 should point at the 001 of the associated bibliographic record. Given the expected support for 001 to be tied to the record ID, we should be able to simply point the 004 at the bib record ID.

• Dan committed r16930 to support this (although we point to the biblio.record_entry.id value, which is more correct anyway).