jsonschema / validation: describe strategies for handling nulls values as if property was unset

[nbolten]

The jsonschema generator currently expects properties that are optional to either exist or not and treats the case of null values as an error case. Many GeoJSON serializers (QGIS, Python's Fiona) may fill values as null when they are undefined (or None, in the case of Python).

We should explicitly decide how to handle this case and/or describe it to downstream users of the provided jsonschema file.