Adding IO examples

src/PythonicAPI.md

src/PythonicAPI/IO/HDRReader.md

src/PythonicAPI/IO/HDRReader.py

src/PythonicAPI/IO/ReadAllPolyDataTypesDemo.py

src/PythonicAPI/IO/ReadExodusData.md

src/PythonicAPI/IO/ReadExodusData.py

src/PythonicAPI/IO/ReadLegacyUnstructuredGrid.md

src/PythonicAPI/IO/ReadLegacyUnstructuredGrid.py

src/PythonicAPI/Snippets.md

src/PythonicAPI/Snippets/DrawViewportBorder.md

src/PythonicAPIComments.md

src/Testing/Baseline/PythonicAPI/IO/TestHDRReader.png

.../Baseline/PythonicAPI/IO/TestReadAllPolyDataTypesDemo.png

src/Testing/Baseline/PythonicAPI/IO/TestReadExodusData.png

...aseline/PythonicAPI/IO/TestReadLegacyUnstructuredGrid.png