[AS7-370] Notification Support

* add notifications to AS7 resources description
  * notifications are described in :read-resource-description operation
    if the notifications boolean is true
  * all resources emit 3 types of notifications by default:
    - resource-added
    - resource-removed
    - attribute-value-written
* NotificationDefinition let any resources describe the notifications
  they can emit by registering them in the ManagementResourceRegistration