Draft: Support to run scripts in container

Instructions in README.md, unfortunately I can't test without messing with projects/translations (i.e. test in production).

Mysql seems to be optional, actually it's not even installed in the server, can we remove the feature that keeps a database of translators?

One thing I know it's broken is sending e-mails, I couldn't make postfix work in the container, if the email sent in case of errors is still relevant I'll need to find a workaround (i.e. use host's postfix from container).