Merge topic 'histrogram-htg'

8cfbd7aa vtkExtractHistogram: Support vtkHyperTreeGrid

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Yohann Bearzi <yohann.bearzi@kitware.com>
Acked-by: Charles Gueunet <charles.gueunet@kitware.com>
Merge-request: !9013