Add information about log and stdout

[goldyfruit]

By default the services will write the logs into a log file under .local directory, this file it not rotated which could lead to disk space issue.

The solution is to add these lines into mycroft.conf, this will tell the services to not create a log file but redirect the logs to the container stdout.

{
  "logs": {
    "path": "stdout"
  }
}

This must be added to the README.md.