Updated the versions of the nifti and znz libs.
First working version of the integration of the new selection mecanism to this version of the app.

Added the SelectionTree, which manages all selection objects and their relationships.

Updated most of related methods in related objects to work with the new structure.

Can now have more than 2 levels of objects.
Removed a debug message.
Fixed crash when deleting an IsoSurface.
Merge branch 'feature_88_Selection' of github.com:jchoude/fibernavigator into feature_88_Selection
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.
Another cleanup pass.

Differents features were updated and cleaned to uniformize
the way they work with the new selection mecanism.
Removed all references to KdTree.

Since it has been replaced by an Octree more than a year ago, time to clean this.
Another pass of cleanup and generalization.
Another cleanup pass, correctin various TODOs.
Removed old TODOs.
Corrected crash on Windows.
Merge pull request #102 from jchoude/feature_88_Selection

Improving the selection mecanism.

Fixes issue #88 and issue #87.