Strip configured fields during import/overlay

Strip configured fields during import/overlay

Records coming in from the staff client may contain junk tags, and
we have a mechanism (not yet exposed) for defining such junk tags
in an inheritable way.  This applies said junk-tag removal based on
said configuration.  The configuration interface is yet to come.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Mike Rylander <mrylander@gmail.com>