Enhance implementation of DOMNotification to deliver event time from Netconf notification to consumer

Notification form Netconf device are delivered as DOMNotification. Interface DomNotification does not contain “event time” from Netconf notification. We need to create implementation DOMNotification that will contain “event time” form original Netconf notification (see https://tools.ietf.org/html/rfc5277#section-2.2) . We recommend to preserve method how to notification are delivered to consumer (DOMNotificationListener). Consumer will be responsible for identification of implementation that contains “event time” and cast it to suitable type.