stretch_deep perception now works with ROS Noetic, Ubuntu 20.04, and
Python 3. The only change for this commit is to two rviz
configuration files that were rendering very large points,
which dramatically slowed down the system.

I tested the following launch files:

stretch_detect_faces.launch
stretch_detect_objects.launch
stretch_detect_body_landmarks.launch
stretch_detect_nearest_mouth.launch

Displaying point cloud points with unusually large sizes in RViz
resulted in a dramatic system slowdown. The face detection
RViz configuration now has a standard small size for the points,
which fixed the problem.