Using GSettings to set for all users

[Richard Hughes <hughsient gmail com>]

I'm about ready to push my gsettings branch of gnome-power-manager
into master. The only remaining bits to port is the "set default"
button which sets the per-user settings for all users. This used to
work using the DBus interface of GConf (the policykit helper), but I'm
unsure on how to port this in a GSettings/dconf world. Ideas welcome.

Thanks,

Richard.