Colorize multispectral dataset point clouds

[Piero Toffanin]

Currently we output point clouds with single band colors for multispectral datasets.

We could improve that by applying colorization from the orthophoto https://pdal.io/en/2.4.3/workshop/exercises/analysis/colorization/colorization.html

Although this is going to be tricky as the orthophoto is the last stage..