color planes should not resize when sash is adjusted

[pieper]

When the slice reformat widgets are visible they track the size of the slice viewers by default. To change this behavior you can adjust the SliceResolution modue for each slice node associated with the plane.

https://github.com/Slicer/Slicer/blob/master/Libs/MRML/Core/vtkMRMLSliceNode.h#L390-L404

SliceResolutionMatchVolumes

@fbudin69500 this is what we discussed on the hangout -- I think you will know where to put this in the code but if not I can have a look.