NcmpEvent creation and Mapping

- Mapping class to create header and event payload based on type of
  operation i.e CREATE, UPDATE and DELETE.
- Service class to get CmHandle public properties, create event and
  delegate request to event publisher.
- Modification in NcmpEvent schema json to mark field as String instead
  of URI
- Test scenarios
- UPCOMING: Call the service method from relevant code to actually
  publish the event.

Issue-ID: CPS-1037
Change-Id: I6bb7de4b27e602c4d8ee6a5528a866e5f7e8799a
Signed-off-by: mpriyank <priyank.maheshwari@est.tech>