Tcal_Enable parameter request

@tridge2,
May I request that 4.1 build should includeimage parapeter just like copter.

Reason:
I am working with Civil Aviation, and one of their requirement for Altimeter is “Programmable based on altimeter setting (in-Hg)”.

I have noticed a big deviation in altitude when flying a plane. Not accurate at all, sometimes off by 200ft.
Since Civil Aviation must work with manned aircraft, they want all UAS to report the correct altitude. I am guessing +/-50 feet deviation is ok.

Thanks for adding this request to the next build.