Changes to field 026 (Fingerprint)

[jenniferward]

Some adjustments are needed to field 026 (Fingerprint):

• Delete subfields $a-$d
• The field should be repeatable.

The field consists of 5 subfields, but in practice $e alone is used the most often, and it's not worth our time to maintain $a-$d. In addition, the field should be repeatable for cases where an edition consists of multiple partbooks.