Add interaction support to vtkPVOrthographicSliceView.

vtkPVOrthographicSliceView now supports double clicking to change the
slice positions in the orthographic views.

Change-Id: Ib41bb84886f2a81efa0788da6fbea066f80b42ec
Merge topic 'orthographic_view_extras' into next

45897e4b Add interaction support to vtkPVOrthographicSliceView.