http://www.devatwork.nl/2007/05/wcf-username-authentication/
http://blogs.msdn.com/b/sonuarora/archive/2007/04/21/setting-client-credentials.aspx
http://blogs.msdn.com/b/pedram/archive/2007/10/05/wcf-authentication-custom-username-and-password-validator.aspx
http://msdn.microsoft.com/es-es/library/system.servicemodel.description.clientcredentials.username.aspx
http://burcakcakiroglu.com/?p=2113