REFACTOR: refactor the SetHead... and SetTail... methods to be more robust
REFACTOR: refactor the SetHead... and SetTail... methods to be more robust

They know set the values even if it is in start or define mode.
However, nothing is done in pose mode as we would have to make sur that
the new position respects a lot of constraint to be sure to be able to
rebuild the pose transform correctly.

vovythevov/Bender-VTK-Widgets,vovythevov/Bender-VTK-Widgets