Adding Python Modelling examples

src/Cxx/ImageProcessing/IsoSubsample.cxx

src/Cxx/Modelling/DiscreteMarchingCubes.cxx

src/Cxx/Modelling/DiscreteMarchingCubes.md

src/Cxx/Modelling/ExtractLargestIsosurface.cxx

src/Cxx/Modelling/ExtractLargestIsosurface.md

src/Cxx/Modelling/MarchingCubes.cxx

src/Cxx/Modelling/MarchingCubes.md

src/Cxx/Modelling/SmoothDiscreteMarchingCubes.cxx

src/Cxx/Modelling/SmoothDiscreteMarchingCubes.md

src/Python.md

src/Python/ImageProcessing/IsoSubsample.py

src/Python/Modelling/DiscreteMarchingCubes.md

src/Python/Modelling/DiscreteMarchingCubes.py

src/Python/Modelling/ExtractLargestIsosurface.md

src/Python/Modelling/ExtractLargestIsosurface.py

src/Python/Modelling/MarchingCubes.md

src/Python/Modelling/MarchingCubes.py

src/Python/Modelling/SmoothDiscreteMarchingCubes.md

src/Python/Modelling/SmoothDiscreteMarchingCubes.py

...ting/Baseline/Cxx/Modelling/TestDiscreteMarchingCubes.png