Add support for deploying backend/api using Docker

[hellais]

We would like to get rid of the debian based deployment and move over to a dockerized approach to make is easier to deploy it on ec2.

We should start off by working on doing this just for the fastpath which is a requirement to being able to move the collector endpoint over to AWS (ooni/backend#931 & ooni/ooni.org#1643).

The order of operations for this should be:

• Get fastpath deployable as a docker container: https://github.com/ooni/backend/tree/master/fastpath
• Get the monolith backend deployable: https://github.com/ooni/backend/tree/master/api
• Define a docker-compose that allows deploying fastpath together with API such that they can communicate to each other

For pieces inside of analysis we should consider moving these over to airflow: ooni/backend#926