Updated Context proto file and related generated code

  SliceId slice_id = 1;

  repeated EndPointId slice_endpoint_ids = 2;

  repeated Constraint slice_constraints = 3;

  repeated ServiceId slice_services = 4;

  repeated ServiceId slice_service_ids = 4;

  repeated SliceId slice_subslice_ids = 5;

  SliceStatus slice_status = 6;

}