move convertDimension out to Dimension::, make getField return a const& instead of a copy for performance win
move convertDimension out to Dimension::, make getField return a const& instead of a copy for performance win

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