Point Cloud change detection with M3C2

[tgoelles]

Maybe implement it as a new method for diff of 2 pointclouds.

cloud compare uses it

Libraries:

https://github.com/ssciwr/py4dgeo
https://www.cloudcompare.org/doc/wiki/index.php/M3C2_(plugin)
https://github.com/lwiniwar/kalman4d & paper: https://esurf.copernicus.org/preprints/esurf-2021-103/