Add doc for pdal split.
Add doc for pdal split.

boundlessgeo/PDAL,boundlessgeo/PDAL,Sciumo/PDAL,mpgerlek/PDAL-old,lucadelu/PDAL,jwomeara/PDAL,DougFirErickson/PDAL,Sciumo/PDAL,mpgerlek/PDAL-old,mpgerlek/PDAL-old,mpgerlek/PDAL-old,DougFirErickson/PDAL,boundlessgeo/PDAL,mtCarto/PDAL,mtCarto/PDAL,lucadelu/PDAL,Sciumo/PDAL,jwomeara/PDAL,mtCarto/PDAL,Sciumo/PDAL,DougFirErickson/PDAL,radiantbluetechnologies/PDAL,radiantbluetechnologies/PDAL,jwomeara/PDAL,radiantbluetechnologies/PDAL,boundlessgeo/PDAL,jwomeara/PDAL,radiantbluetechnologies/PDAL,lucadelu/PDAL,mtCarto/PDAL,DougFirErickson/PDAL,lucadelu/PDAL