Show the dual point correspondence in dual return.
Show the dual point correspondence in dual return.

In dual return mode, add a spreadsheet column showing the id of the dual
point of each point, when there is one.

See internal merge request 19
Kitware/VeloView,Kitware/VeloView,Kitware/VeloView,Kitware/VeloView,Kitware/VeloView