I noticed I couldn't edit NetworkManager settings in XFCE, and it turns it
there is no polkit authentication agent running. Every desktop seems to
have their own one, and XFCE seems to use polkit-gnome. Since it was 
abandoned by GNOME it isn't used for anything else. So I setup an autostart
desktop file just like how mate-polkit has one.
It feels a bit odd configuring the package with an embedded desktop file
just for XFCE. Perhaps it would be better to put it in a separate "xfce-autostart"
output or just put it into the xfce package instead of the polkit-gnome package.

What do you think?