Update docker images to modify mysql configuration

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.

docker/my.cnf

@@ -0,0 +1,4 @@
+[mysqld]
+log-basename=bin
+log-bin=/var/lib/mysql/logs/bin
+binlog-do-db=streamline