[QnA Maker] Multi-turn support for python

[gurvsing]

Multi-turn support for python

[Zerryth]

@trojenguri its build is failing on linting issues

Please pip install black and pylint, then run the following commands on your code from root of repo:

• black libraries
• pylint --rcfile=.pylintrc libraries

so that it'll auto-format your code to the repo's rules and also give you the linting errors that'll need to be fixed for the build to pass:

[Zerryth]

Nice PR! Excited for the multi-turn feature to be folded into the SDKs

Mostly just linting issues that need to be addressed. Also feel more comfortable if @axelsrz , our Python repo champion, takes a look at the PR as well.

[axelsrz]

Hello @trojenguri nice PR! I would like to merge this whenever @cleemullins takes the C# and JS ones.

[cleemullins]

Please increase code coverage metrics.

changes addressed