Mean fiber now working.

Updated the mean fiber computations and display code to make them work
with the new stats pipeline.
Removed old code that was not needed anymore.
Cleanup of unused parts, following refactoring.

Some methods and members were not needed anymore.
Part of cleanup of this.
Removed the computation of mean curvature and torsion.

Thoses 2 statistics were almost meaningless when selecting fibers, so I removed
them. Methods that were still used when coloring using the torsion and the curvature
were moved to the Helper class.