Clicking on menu item selects the sensor shown in panel.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'

Conflicts:
	extension.js
Added 'Average' and 'Maximum' as sensor entries

Removed specific setting to show average or maximum temperature in
panel, just treat them as a sensor.
Selected sensor to show in panel is now called 'main-sensor' in the
settings and it's also highlighted in bold in the menu list.
Fixed 'main-sensor' setting description and default