Allow application to be started in the system tray only when started with
the `-t' command line argument.
Signed-off-by: Kel Modderman <kel@otaku42.de>
Do not connect lastWindowClosed() to quit(), instead explicitly close the
application if File->Exit or window manager close button is activated.
This allows the tray app to avoid being closed with last visible window,
and launch scan and event history windows individually.
Signed-off-by: Kel Modderman <kel@otaku42.de>