Support restarting replication on server restart

[fulghum]

By default, MySQL will automatically restart replication when a server comes up, if replication was enabled before it was shutdown. For example, if a MySQL server is started, the replication source is configured, and then start replica; is called, the server will automatically start up replication the next time it is started (assuming stop replica; is not called first). Dolt should implement this same behavior.