title: estimateRigidTransform missing from 3.5+
body: <p>I have moved from 3.4 to 4.0 and cv2 is missing the estimateRigidTransform function. The documentation shows it is still there in the C++ library but it is not in cv2. Has it been renamed or am I missing something stupid when im building it?</p>
  
  <p>I checked 3.5 and it looks like it is the first version where it is missing.</p>