Adc routing removal

This removes the ADCRouting layer of indirection when using the ADC pins. It is
much cleaner to simply have the pin selection in the appropriate UAVO (and removes
an unnecessary and bulky UAVO). It also makes the code much cleaner instead
of looping over all possible pins to see which is assigned a task.

This was a weird way to do it as suddenly the settings for things like battery
were spread through two objects.

Incidentally, this makes the FlightBattery calculation pick up changes in the ADC
assignments at runtime.

Fixes #1047