Add Gunicorn WSGI Server

[alanvitor]

This pull request adds Gunicorn WSGI Server to handle Flask App and fixes some flask app config.

[Terrtia]

Thank you for the pull request !

I have concerns about potential performance issues.
benoitc/gunicorn#2596
AIL chat feeders are sending large JSON payloads to the API.

Have you encountered any issues with the Flask app configuration?

[alanvitor]

I was not aware about this issue in Gunicorn. Have been working with Gunicorn and uWSGI a couple of years and didn't get something like that. Tell me the average size of this payload and I can perform some tests and post it here.

The issues with config was the bind ip address set to 127.0.0.1, and the https in ail_domain.

With 127.0.0.1 it was unable to reach the application from load balancer; and tls certificate is attached to load balancer instead of application.

[SteveClement]

please do not change core configs if not needed.