Got my first automatic registration (rotation) and as a bonus, height of ceiling.
I had to set the PLANE RANSAC threshold to 0.02  in order to capture small orthogonal
planes to the main planes in the ceiling. Problem: how to make this work in general.

Seeking lines within planes will not work because the Kinect has a natural scan direction,
so false lines will likely be found, which are not physical.

Consider applying  clustering algorithm to each plane to identify which planes corespond
to solid planes, and which planes are the "false" result of objects in the scene aligned
by chance to form a plane.

Consider some kind of multi-scale approach. Start with higher thresholds, and go towards
lower thresholds. I am not sure, intuitively of how well that would work.