Fix authenticated SMTP configuration

To use auth in smtp configuration need to change configuration file format to groovy, because mail.smtp.auth is a propertie in a array, but is not supported by properties file. Mail configuration reference: http://grails.org/plugin/mail

Example of configuration in groovy format: https://gist.github.com/gschueler/5707281

This work for me. I am using AuthSmtp provider.