Add lightdm to mesh/usb installs

src/freedombone-image-customise

@@ -1069,7 +1069,7 @@ function configure_user_interface {
 	fi
 
 	# desktop
-	chroot "$rootdir" apt-get -y install mate-desktop-environment
+	chroot "$rootdir" apt-get -y install mate-desktop-environment lightdm
 
 	# browser
 	chroot "$rootdir" apt-get -y install iceweasel