Bug 17913: Use replace_with instead of insert_grouped_field

Bug 17913: Use replace_with instead of insert_grouped_field

Original fix from a patch on bug 5572.
Amended by Marcel de Rooy January 2017.

Note: This does not yet resolve the field order when merging to another
auth type, but is a good start.

Test plan:
Run t/db_dependent/Authorities/Merge.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>