Add docker composition //DO NOT MERGE!

[XaviTorello]

It provides a docker-composition that deploys this project using:

• db container
  • integrates a Postgresql (postgis-ready)
• web container
  • using our own build definition over this repo starts our django (pre-processing the requirements and applying pending migrations)
  • waits for the availability of the DB service using wait-for-it.sh

Django settings has been ammended to ensure that everything works as expected (postgres engine config, allowed_hosts, ...)

Composition vars are integrated inside the .env file

Fix #2 Provide a Docker composition