Update and move old python plotting scripts from `IW2D/cpp`
The 'IW2D/cpp' folder should be for C++ related files only, so the old plotting scripts can be moved, for example to 'IW2D/legacy'.
The 'IW2D/cpp' folder should be for C++ related files only, so the old plotting scripts can be moved, for example to 'IW2D/legacy'.