those whose string ref syntax is unknown or can't be guessed i.e.
don't use it for new documents (prefer user settings in that case)

Change-Id: I1355031cdd63e2a5c50064531011be71ae7f7b8f
Reviewed-on: https://gerrit.libreoffice.org/18923Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>