Added the possibility to provide the sendmail location in NOTIFICATION_SENDMAIL_MAILER.

Added NOTIFICATION_STORAGE_MAILER which allow to store the email in a storage (could be just output, file, database ...)
Added SMTP implementation, based on EiffelNet SMTP_PROTOCOL.
   note: it is possible to exclude this by setting ecf variable "smtp_notification_email_disabled" to "True"
   this way help to manage dependencies, since the Eiffel Net library would not be included neither.
Fixed Date header value computation.

library/runtime/process/notification_email/notification_null_mailer.e

@@ -0,0 +1,34 @@
+note
+	description: "Mailer that does nothing."
+	date: "$Date: 2015-06-30 15:49:56 +0200 (mar., 30 juin 2015) $"
+	revision: "$Revision: 97588 $"
+
+class
+	NOTIFICATION_NULL_MAILER
+
+inherit
+	NOTIFICATION_MAILER
+
+feature -- Status
+
+	is_available: BOOLEAN = True
+			-- <Precursor>
+
+feature -- Basic operation
+
+	process_email (a_email: NOTIFICATION_EMAIL)
+			-- <Precursor>
+		do
+		end
+
+note
+	copyright: "2011-2015, Jocelyn Fiat, Javier Velilla, Olivier Ligot, Eiffel Software and others"
+	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
+	source: "[
+			Eiffel Software
+			5949 Hollister Ave., Goleta, CA 93117 USA
+			Telephone 805-685-1006, Fax 805-685-6869
+			Website http://www.eiffel.com
+			Customer support http://support.eiffel.com
+		]"
+end