Add read_json to SessionContext

[larskarg]

Related to #28.

MR adds functionality to read json files. I have added some tests cases (not all parameters are covered). Please let me know if the test cases are sufficient and/or if I should store the test data differently.

Example:

importdatafusionctx=datafusion.SessionContext()
df=ctx.read_json("data.json")
df.show()

[francis-du]

LGTM

[andygrove]

Thanks @larskarg

[andygrove]

@larskarg It looks like there is a Python lint issue and also needs an upmerge

[larskarg]

@andygrove

Upmerge done.

I did also run

flake8 --exclude venv --ignore=E501
black --line-length 79 --diff --check .

locally but didn't see any Python lint issues. Unfortunately, I cannot trigger the github workflow as a first-time contributor. Can you please point me to the Python lint issue? Thanks.

[francis-du]

🎉