Bug 18904: (follow-up) Retrieve subfield in the order they are stored

Bug 18904: (follow-up) Retrieve subfield in the order they are stored

Use subfields in the order they are stored.

This patch removes use of an intermediate hash for storing values. Order
of subfields as obtained from authority is now preserved.

Also removes useless code that was intended to set $2 subfields

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>