Update global Firefox icon instead of per-window state
Update global Firefox icon instead of per-window state

When we set the uProxy icon for Firefox, update the global icon state
across windows instead of trying to limit the change to a single window

Fixes #1292

jpevarnek/uproxy,roceys/uproxy,dhkong88/uproxy,uProxy/uproxy,chinarustin/uproxy,MinFu/uproxy,dhkong88/uproxy,dhkong88/uproxy,itplanes/uproxy,uProxy/uproxy,dhkong88/uproxy,itplanes/uproxy,jpevarnek/uproxy,roceys/uproxy,qida/uproxy,itplanes/uproxy,MinFu/uproxy,itplanes/uproxy,uProxy/uproxy,uProxy/uproxy,roceys/uproxy,MinFu/uproxy,itplanes/uproxy,qida/uproxy,IveWong/uproxy,jpevarnek/uproxy,IveWong/uproxy,roceys/uproxy,jpevarnek/uproxy,qida/uproxy,MinFu/uproxy,IveWong/uproxy,uProxy/uproxy,chinarustin/uproxy,MinFu/uproxy,qida/uproxy,roceys/uproxy,qida/uproxy,IveWong/uproxy,dhkong88/uproxy,jpevarnek/uproxy,chinarustin/uproxy,chinarustin/uproxy,chinarustin/uproxy