Log Message:
Update xfce4-netload-plugin to 1.3.1:

1.3.1
=====
- Set progressbar minimal width and height depending on the orientation \ 
(#12941,#12949)
- Apply css on the correct widget class for Gtk 3.16/3.18
- rework the use of GtkCssProvider to use a singleton
- da and oc translation updates

1.3.0
=====
- Fix progress bar grow direction in deskbar and vertical modes
- set progressbar minimal width/height to 4px so that it looks like with gtk+2