Assign a volume to persist orders on restart

[dekz]

Assign a volume to backend so that orders are persisted across restarts.

Document a production ready database.

Database currently lives inside the container in the working directory as database.sqlite. To make a copy of the database run:

docker cp <container id>:/usr/src/app/database.sqlite .

[dekz]

This is now possible and an answer has been added to the FAQ.