Undo redo registration feature

This merge adds the itkRegistrationAddOn lib of vtkinria3d which contains
several classes that could be useful to the RPI. ,
This library is used for the undoRedoRegistration feature (cf http://pm-med.inria.fr/issues/1146).
In this patch, we also merge the vtkinria3d version of itkDisplacementFieldTransform and the RPI's version.

In the first commit, we correct a small mistake with indices in the latex explication of RPI.

Reviewers : Guillaume, Olivier
Merger : Olivier

This merge request is linked to three different merge requests : 
One in medinria-plugins : https://github.com/medInria/medInria-plugins/pull/11
One in medinria : https://github.com/medInria/medInria-public/pull/9
One in medinria-plugins-private http://dev-med.inria.fr/medinria-asclepios/medinria-plugins-private/merge_requests/2