Dockerfiles are updated with two key changes:
- use streamline's official images as a base
- replace two files related to mysql configuration
A README.md file is added to the docker folder which details the changes, but
the key difference is to limit binary logs to only the `streamline` database.
This prevents additional system databases from being included, which the
database sync tools do not (yet) support.
An unrelated bugfix corrects the docker-compose image tag, specifying 'latest'
instead of a previously hard-coded version.
