Potentially wrap email block so we can send emails to github users

[phillipjohnston]

We know that the Emails information coming from GIT is correct (close, controled environment) so we disable the "not sending mail to unregistered user" by using a variable included in the EmailExt plugin version 2.58, introducing following code:

def currenVal = RecipientProviderUtilities.SEND_TO_UNKNOWN_USERS
RecipientProviderUtilities.SEND_TO_UNKNOWN_USERS  = true
// Send Email with emailext
RecipientProviderUtilities.SEND_TO_UNKNOWN_USERS = currenVal

(this needs to include import hudson.plugins.emailext.plugins.recipients.* and also needs a securiy confirmation)