Volume control difficult to detect for newbies

[jondo]

I have used Chorus2 for the first time today, and it took me a long time to detect the volume control. Finally I found the issue #242, from which I learned the necessary keypad keys, and by changing the volume with these keys I managed to detect the changing volume in the GUI.

To keep the GUI minimal, this could also be described in a 'users guide' (#143).

[ninovanhooff]

Also the graphical grey bar above the mute, repeat etc buttons because it's not visually distuingishable from the other elements