Defining backend separately allows e.g. creating ADMX templates with
easy-to-use UI, where user defines only LDAP names for the setting, and
doesn't need to type the LO configuration backend name.

Change-Id: I64f23043c94a5a4e0ba7281d0f711a427d694126
Reviewed-on: https://gerrit.libreoffice.org/53413Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>