Fixed various errors. I can read a non-RGB cloud and store it in an RGB cloud.
Created a function to set a cloud to a particular color
Created a function (not debugged) to display two clouds, one per viewer, for pairwise registration.
When applying filters, limit clouds to 40,000 points. (perhaps that should be changed to only compute
a maxiumm of 40,000 normals (at least on my mac).