Fix camera Elevation and Pitch if angle is 90

If the Elevation or Pitch angle is 90, there will be a cross product in vtkPerspectiveTransform::SetupCamera that generates a (0,0,0) vector, leading to the scene to disapear.

To avoid that, the ViewUp vector must be updated before the computations, but restored to its previous state since we do not want the ViewUp to be modified after the call. (see discussion here: http://vtk.1045678.n5.nabble.com/Bug-in-vtkCamera-Elevation-td5736357.html)

cc: @dgobbi @ben.boeckel