Reply a status when authentication is required in the bridge socket

This pull request concern only the bridge socket. As far as I understand it, if a person is not authenticated or allow to access to a eventbus address, the message is juste ignore and the client keep waiting. For my understanding, I think It would be interesting to send that information to the client :

  * access_denied : when the user is authenticated but not allow
  * auth_required : when the user is not authenticated
  * auth_error : when we are enable to get user authentication information

This a suggestion of implementation because I really don't know if the I reply is a good or the best way.
Best regards,
Maneau