Work in progress to allow integration of LO with
<https://wiki.gnome.org/Projects/FleetCommander>.

During configuration, dconf support is implicitly enabled when available on the
host (which is presumably only available on Linux).  It is explicitly disabled
for TDF Linux builds for now, though, to avoid accidental dependencies of the
distributed installation sets on system dconf libraries.

A dconf layer is represented in the CONFIGURATION_LAYERS bootstrap variable with
type "dconf" and an empty URL.  See the comment at the top of
configmgr/source/readdconflayer.cxx for the encoding of component-data in dconf.

All of this is still subject to change.

Change-Id: I2d08d81c8ea43ba4a99040a8882ae75b91bcfdb9
Reviewed-on: https://gerrit.libreoffice.org/16848Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>