Using itk::VectorImage instead of itk::Image<Vector<...

[fbudin69500]

Using itk::VectorImage instead of itk::Image (and the corresponding itk::Dream3DImage) with vector components would allow to not hardcode the number of dimension for vectors, and therefore not limit the user to a small number of vector images that can be processed (currently only vectors of dimension 2 and 3 are accepted).