Adding MarkKeypoints, CaptionActor2D

src/PythonicAPI.md

src/PythonicAPI/IO/ImportToExport.py

src/PythonicAPI/ImageProcessing/HybridMedianComparison.py

src/PythonicAPI/Images/MarkKeypoints.py

src/PythonicAPI/Images/TestMarkKeypoints.png

src/PythonicAPI/Picking/HighlightPickedActor.py

src/PythonicAPI/Picking/HighlightWithSilhouette.py

src/PythonicAPI/Visualization/CaptionActor2D.py

...Testing/Baseline/PythonicAPI/Images/TestMarkKeypoints.png

...Baseline/PythonicAPI/Visualization/TestCaptionActor2D.png