Datastore: please support specifying read consistency

[rvandegrift]

According to the Cloud Datastore docs, the python client does not support setting the read consistency of a query:
https://cloud.google.com/datastore/docs/concepts/structuring_for_strong_consistency#datastore-eventual-consistent-query-python

Any chance this could be implemented?

[dhermes]

Yes, and it would only need to be changed in one place for the underlying implementation.