RC3 usually used as Throttle, but trim was set to 1500 by default.
It should be 1000 by default.
There were unintialized variables.
(control mode was not updated)

Also, new flags (xy_valid etc) were considered.
Airframe No. 21. 22 have been added.
That is for general ESC with PX4IO (frame geometry defined)
Update sensor_params.c

Not necessarily modify this on initial.
Merge pull request #426 from limhyon/master

PX4Flow, and several tiny things enhanced.