Modernising the code, improving images

src/Cxx/PolyData/AlignFrames.cxx

src/Cxx/PolyData/AlignTwoPolyDatas.cxx

src/Cxx/PolyData/AlignTwoPolyDatas.md

src/Cxx/PolyData/AttachAttributes.cxx

src/Cxx/PolyData/BooleanOperationPolyDataFilter.cxx

src/Cxx/PolyData/BooleanOperationPolyDataFilter.md

src/Cxx/PolyData/Casting.cxx

src/Cxx/PolyData/Casting.md

src/Cxx/PolyData/CellCenters.cxx

src/Cxx/PolyData/CellCentersDemo.cxx

src/Cxx/PolyData/CellEdgeNeighbors.cxx

src/Cxx/PolyData/CellEdgeNeighbors.md

src/Cxx/PolyData/CellLocator.cxx

src/Cxx/PolyData/CellLocator.md

src/Cxx/PolyData/CellLocatorVisualization.cxx

src/Cxx/PolyData/CellLocatorVisualization.md

src/Cxx/PolyData/CellPointNeighbors.cxx

src/Cxx/PolyData/CellPointNeighbors.md

src/Cxx/PolyData/CellTreeLocator.cxx

src/Cxx/PolyData/CellsInsideObject.cxx