Pushed new branch to rMITK MITK: feature/T28578-MxN-development.

I stumbled upon this again as I was working on an issue with the SliceNavigationController. I suggest to remove the QmitkSliceBasedInterpolatorWidget completely as it is not used anymore.
@s349i is making his changes inside QmitkSlicesInterpolator. As far as I remember QmitkSliceBasedInterpolatorWidget was the interpolation-widget used inside the QmitkMultiLabelSegmentationView, which was removed when the two segmentation views were merged (see 6582705bee86).

I found a line of code where the function is actually used:
Inside QmitkImageNavigatorView::SetStepSize:

if (m_IRenderWindowPart)
{
  mitk::BaseGeometry::ConstPointer geometry = m_IRenderWindowPart->GetActiveQmitkRenderWindow()->GetSliceNavigationController()->GetInputWorldGeometry3D();