ENH: WIP: #3788 Add path for reading itkBSplineTransform (for ITKv4)

Mostly implemented but the transform that gets read in is identity
and not the one in the file.  Probably something wrong with
this cast:

+  typedef itk::BSplineTransform< T,VTKDimension,BSPLINE_TRANSFORM_ORDER > BSplineTransformType;
+  typename BSplineTransformType::Pointer bsplineItk =
+    dynamic_cast< BSplineTransformType* >( warpTransformItk.GetPointer() );