Add "time-stamp" data at the begin of a received mail

When receiving a new mail, create a new file with the time-stamp.
Typically:
        Received: FROM sender.io WITH SMTP
            BY smtp.server.io
            ; 21 Jun 2013 13:04:45 (BST)

Also update the Email data structure:
- mailFrom: is now a Maybe ReversePath. So it is easier to manage errors.
- smtpType: add this field to now if the client is connected with SMTP
  or ESMTP.

Also update the way to parse the MailStorageUser configuration file (use
configurator now).
DeliveryManager: local part

Implement a small service to copy the mail data to the local recipients.

Incoming: forward the mail to the distant recipients.