BUG: VR fixes for VTK 9

CMake/External/External_VTK.cmake

CMake/iMSTKConfig.cmake.in

CMakeLists.txt

...ples/PBD/PBDCollisionStairs/PBDCollisionStairsExample.cpp

Examples/PBD/PBDString/pbdStringExample.cpp

Source/Rendering/CMakeLists.txt

...Renderer/RenderDelegate/imstkVTKCapsuleRenderDelegate.cpp

Source/Rendering/VTKRenderer/imstkVTKRenderer.cpp

Source/Rendering/VTKRenderer/imstkVTKRenderer.h

Source/Rendering/imstkVtkCapsuleSource.cpp

Source/Rendering/imstkVtkCapsuleSource.h

Source/Rendering/vtkCapsuleSource.cpp

Source/SimulationManager/VTKRenderer/imstkVTKViewer.cpp

Source/SimulationManager/imstkSimulationManager.cpp

Source/SimulationManager/imstkSimulationManager.h