Add more Python API documentation

Merged Morten Ofstad requested to merge feature/morten.ofstad/AddMorePythonAPIDocumentation into master

Added openWithAdaptiveCompressionTolerance/openWithAdaptiveCompressionRatio calls, DMSOpenOptions/VDSFileOpenOptions, VolumeDataRequest and VolumeDataPageAccessor/VolumeDataPage classes to the python-api.rst file.

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