Modernising the code, improving images

src/Cxx/PolyData/CMakeLists.txt

src/Cxx/PolyData/DataSetSurfaceFilter.cxx

src/Cxx/PolyData/DataSetSurfaceFilter.md

src/Cxx/PolyData/EmbedPointsIntoVolume.cxx

src/Cxx/PolyData/ExternalContour.cxx

src/Cxx/PolyData/ExternalContour.md

src/Cxx/PolyData/ExtractCellsUsingPoints.cxx

src/Cxx/PolyData/ExtractOutsideSurface.cxx

src/Cxx/PolyData/ExtractOutsideSurface.md

src/Cxx/PolyData/ExtractPolyLinesFromPolyData.cxx

src/Cxx/PolyData/ExtractPolyLinesFromPolyData.md

src/Cxx/PolyData/ExtractSelectedIds.cxx

src/Cxx/PolyData/ExtractSelectedIds.md

src/Cxx/PolyData/ExtractSelection.cxx

src/Cxx/PolyData/ExtractSelection.md

src/Cxx/PolyData/ExtractSelectionCells.cxx

src/Cxx/PolyData/ExtractSelectionOriginalId.cxx

src/Cxx/PolyData/FieldData.cxx

src/Cxx/PolyData/FieldData.md

src/Cxx/PolyData/FitSplineToCutterOutput.cxx