New PnP approach to calib3d module

SOLVEPNP_UPNP

Method is based on the paper of A.Penate-Sanchez, J.Andrade-Cetto, F.Moreno-Noguer. "Exhaustive Linearization for Robust Camera Pose and Focal Length Estimation".

Usng this method estimates the camera pose and the parameters fx and fy assuming that both have the same value. Then the ``cameraMatrix`` is updated with the estimated focal length.
please, add the standard OpenCV license and optionally your copyright/info. Also, please, use some prefix in the guard macro, e.g. OPENCV_CALIB3D_UPNP_H instead of UPNP_H.