tckmap: Added option groups
tckmap: Added option groups

Diving the tckmap options into groups makes the help page more readable, and also forces a more appropriate clustering of these options.

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3