[CF-metadata] accessory parameters

[Jonathan Gregory]

Dear Roy and Nan

Thanks for your careful discussion.
> 
> I realize we're not chosing a "rule" but just a parameter name; it'd be
> good to do it in a way that could be appplied consistently anyway.
Quite right. Of course, if we find on longer experience that we got it wrong,
we can change our minds and use aliases for older names.

> 'sensor_temperature_oxygen_in_sea_water.'

I think I'd prefer it to be a bit more of a phrase in English, to be clearer
what goes with what. Would temperature_of_sensor_for_oxygen_in_sea_water
be acceptable?

best wishes

Jonathan