ENH: Improving the comparative visualization view and gui.
Improved the Comparative Viz panel making it easier to add parameter values for explicit locations in the comparative view. Improved vtkSMComparativeViewProxy to automatically update all the views each time it renders. Added mechanism to ServerManager to write Proxies that don't provide the traditional properties API and yet participate in state save/restore and undo/redo. Look at vtkSMComparativeAnimationCueProxy as an example.