I agree with the name suggestion, since it has nothing to do with the `sender` of the message, but the location of the mediator

AFAIK it is not necessary to use a new message class. Isn't this alright?

    case class SendToAll(path: String, msg: Any, allButSelf: Boolean = false) {
      def this(path: String, msg: Any) = this(path, msg, allButSelf = false)
    }