Support for basic Master-Slave Replication on 5.6

[ioggstream]

Actual images does not support replication parameters.

This patch supports the following variables:
+# - MYSQL_ROOT_PASSWORD
+# - MYSQL_REPLICA_USER: create the given user on the intended master host
+# - MYSQL_REPLICA_PASS
+# - MYSQL_MASTER_SERVER: change master on this location on the intended slave
+# - MYSQL_MASTER_PORT: optional, by default 3306
+# - MYSQL_MASTER_WAIT_TIME: seconds to wait for the master to come up

You can test the resulting image with the fig.yml present here https://registry.hub.docker.com/u/ioggstream/mysql/

[yosifkit]

I'll defer to @ltangvald as to whether we want to add such functionality to the image.

Closing old issue, if you feel this was closed in error please let us know.

[ltangvald]

I think it's better to handle this with the init system.

Though as these fairly common use-cases keep coming in maybe we could have an examples section in the repo with some simple scripts that demonstrate how to do them.