Add parameter keys to command line arguments about potreeconverter HOT 1 CLOSED

usage: PotreeConverter [OPTIONS] SOURCE
Options:
  -h [ --help ]             prints usage
  -o [ --outdir ] arg       output directory
  -s [ --spacing ] arg      Distance between points at root level. Distance
                            halves each level.
  -l [ --levels ] arg       Number of levels that will be generated. 0: only
                            root, 1: root and its children, ...
  -f [ --input-format ] arg Input format. xyz: cartesian coordinates as floats,
                            rgb: colors as numbers, i: intensity as number
  -r [ --range ] arg        Range of rgb or intensity.
  --source arg              Source file. Can be LAS, PLY or XYZ

./PotreeConverter.exe C:\data.ply
./PotreeConverter.exe C:\data.ply -o C:\conversion
./PotreeConverter.exe C:\data.ply -o C:\conversion -s 0.1 -l 2