refactor: update transformation system, improve template readability, and reorganize VTK assembly management

src/Vtk/Math/vtkVoxImage.h

@@ -31,6 +31,7 @@
 #include <vtkVolume.h>
 #include <vtkXMLImageDataReader.h>
 #include <vtkXMLImageDataWriter.h>
+#include <vtkAssembly.h>
 
 #include <Math/VoxImage.h>
 
@@ -77,6 +78,7 @@ private:
   vtkImageData *m_Image;
   vtkCubeSource *m_Outline;
   vtkActor *m_OutlineActor;
+  vtkAssembly *m_Asm;
 
   vtkXMLImageDataReader *m_Reader;
   vtkXMLImageDataWriter *m_Writer;