keyboard shortcuts for pavucontrol

[halim.sahin@xxxxxxxxxx (Halim Sahin)]

Hi Col,
I havent looked in the code but it wiould be enough to add a shortcut
for opening the contextmenu for moving the streams.
like shift+f10

I am able to tab to the label of the stream so it should be possible to
add the shortcut if the streamlabel is selected.

Thanks
Halim