LAS format support

From a user voice request.

Add support for .las LAS file format, specifically xyzRGB:

Laser scanning data are typically in xyzRGB format, where xyz are the coordinates and RGB are columns for the R, G, and B colours (values from 0…255 for each). The current support for only one colour field could be extended to define the colours through three different fields. In addition, laser scanning data, i.e. point clouds, may contain points up to billions, in which case long coordinates may hinder the calculation time needed for the visualisation. Therefore it is suggested to build an filter or process that only takes into account the changing parts of the coordinates.

Currently there is a plugin for it in lidarview:

Also, some fonctionnality may be available already:

Indeed, LAS support can be extended. PDAL reader could be used instead but that is not included with the ParaView binary yet.