Suggest use of system tray as an option

[Rashidwi]

Gnome no longer has a system tray and qpwgraph attempting to use this causes some rather odd problems, somehow related to the black on black problem earlier discussed.

I've re compiled without the tray (once I saw there was an option ;) and it's much better.

It would be ideal if qpwgraph could either detect if it's running under Gnome and not use the system tray, or at least make a command line option.