Re-apply the changes provided by  0802 for backport

Preserve record order of subfields for authority heading extraction

When extracting headings from authority records we currently read the
subfields of a tag in configuration order.  We should, instead, read
them in record order, to preserve the desired sorting properties that
the cataloger has encoded in the record.

Signed-off-by: Mike Rylander <mrylander@gmail.com>