Add support for running service in Docker container

- Provide Dockerfile to build and run the service in container
- Using environment variables for config
- Supporting also .env to provide config
- Updated documentation accordingly
1) Please, see my previous comment about `-P` vs `-p 5000:5000`
2) Why -i here? Do we need to be interactive?
3) Could you point somewhere explaing why the need of the `-t`? We need a pseudo-tty?