BUG #15867: Parallel projection wasn't restored from settings.
The problem was that the parallel projection mode was getting overridding in vtkPVRenderView when initializing the interactor after the property values had been loaded from settings. Hence we UI showed correct value for parallel projection, however the Camera was still doing perspective projection.
Since vtkPVRenderView changes parallel projection mode internally, it makes sense to update the RenderView proxy XML to not directly set parallel projection mode on the vtkCamera but instead pass it via vtkPVRenderView. Thus, vtkPVRenderView can cache it and restore it correctly when interaction mode is changed.