Fix vtk6 integration

This PR fixes a few issues found after migrating to VTK 6 demand driven pipeline.

1. Fix Connection topology issues in Cutter, Outline Filter and Probe Filter.
2. Fix vtkInformationRequest for data objects failed in flight graph and picker examples. 
3. Fix could not generate normals warning thrown by vtkTubeFilter by using vtkCleanPolyData filter
Is this really needed?  Can the tvtk.common API be used to do this?