Add ballista python module

[nl5887]

Rationale for this change

This will introduce the ballista python module, similar to the datafusion python module.

[andygrove]

Thank you for the contribution @nl5887. Having a Python repl as part of Ballista will make it much more accessible.

Because this builds on the datafusion-python module which was originally part of DataFusion but is now part of the datafusion-contrib GitHub org (outside of Apache Arrow governance) I need to figure out what the IP clearance situation is for this contribution.

One option may be for us to restore the original datafusion-python code here from before it was removed from this repo and then rebase your PR so it just has the additions on top of that. Another option will be for us to treat it like a regular donation which will require getting all contributors to sign an ICLA (or remove their contributions from the donation).

[andygrove]

@thinkharderdev @yahoNanJing @realno @Ted-Jiang fyi

[thinkharderdev]

Nice! This is a great contribution.

[jimexist]

this won't work - it has only 0.12.10 pushed to dockerhub

[andygrove]

@nl5887 Now that #61 is merged, could you rebase this PR on top of that, with the code going into the python directory rather than ballista-python. This will allow us to see the specific changes that are being contributed.

[nl5887]

@andygrove rebased this PR on top of #61. The conflicts shows how datafusion-contrib and this python converged.

[andygrove]

Hi @jimexist. Now that we have restored the original DataFusion Python bindings in this repo, would you be willing to create a PR here to submit the improvements that you have made in the datafusion-contrib repo? That will reduce the size of this PR further. We need to be careful not to include changes from contributors that have not yet signed an ICLA but as far as I can see there are just two such commits and they could easily be excluded. If you don't have time to do this would you be ok with me creating the PR with your changes? Thanks.

[andygrove]

Hi @jimexist just in case you missed the previous message. Let me know what your thoughts are,

[andygrove]

Hi @nl5887 Sorry for the delay on this but there have been discussions on the mailing list about this and it turns out that we can just go ahead and PR these changes after all. Would you mind rebasing this PR and I can go ahead and review. Thanks for your patience.

[andygrove]

It's been just over a month without activity so I will close this in favor of #157

Thanks for the help with this @nl5887 - I used the ballista context code from this PR