Get pose from camera params using opencv2

[raphaelmemmesheimer]

I think there were some leftovers from the past. I changed the fromCameraParams function to work with opencv2.

[tfoote]

Thanks for looking to modernize this. However I have to ask if this is backwards compatible. In particular a CvMat and a Numpy array I believe are not interchangeable. So this would be a noticeable change in API which would break any current users. To that end I might suggest considering creating a new related function. However in general this whole repository is generally deprecated in favor of geometry2. So to that end I'd suggest looking to contribute this similar functionality to tf2_kdl.

https://github.com/ros/geometry2/blob/melodic-devel/tf2_kdl/src/tf2_kdl/tf2_kdl.py

The one other caveat is that that doesn't have an opencv dependency so there might be a better place for it such as image_geometry. Though that doesn't have a dependency on kdl so this functionality falls somewhere in between.