Adapt to QVTKOpenGLWidget changes in VTK
Adapt to QVTKOpenGLWidget changes in VTK

It now does quite a bit more, there is no need to create a render window
anymore. Hopefully this works across all platforms now, issue #1878 is
quite possibly related to render window initialization.

Signed-off-by: Marcus D. Hanwell <cf7042e2e8eee958b5bcde1ae2cbefef82efc184@kitware.com>

OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz