_finalize methods need information which is not available if all you
have is a mavlink_message_t

before, with a version of eg. 1.5.0, the user was wrongly notified.

Sony a6000 ILCE-6000 with 16mm lens.
Source : 
http://www.sony.co.uk/electronics/interchangeable-lens-cameras/ilce-6000-body-kit#product_details_default

-fixes #4073

it's not a typical APS-C sensor, proper size gives more accurate
calculations.

-fixes #4035

The 22mm as stated on the lens is actual, not 35mm equvalent as on smaller
cameras.  - So it was wrong to reverse calculate for crop factor.

This reverts commit ae976049ca7b4818616e6b8be07a028fc7dfc26f.