Combine two camera arrays
in_cameras1.json in_cameras2.json out_cameras.json [common_camera]
Output out_cameras.json will contain cameras from both inputs. If camera with same name exists in both arrays, the one from in_cameras1.json is taken.
Can also be used to put two camera arrays into one global coordinate system: common_camera may be set to the name of a camera that occurs in both input arrays. If set, then the cameras from in_cameras2.json are first transformed such that the extrinsic of common_camera in in_cameras2.json becomes the same as that in in_cameras1.json.