Add polygon to DTO convert strategy

DataAccess/DTOs/DTOEntities/NdmCrossSections/EllipseNdmPrimitiveDTO.cs

@@ -11,6 +11,11 @@ namespace DataAccess.DTOs
     {
         private IRectangleShape shape = new RectangleShapeDTO(Guid.Empty);
 
+        public EllipseNdmPrimitiveDTO(Guid id)
+        {
+            Id = id;
+        }
+
         [JsonProperty("Id")]
         public Guid Id { get; set; }
         [JsonProperty("Name")]
@@ -42,7 +47,7 @@ namespace DataAccess.DTOs
 
         public object Clone()
         {
-            throw new NotImplementedException();
+            return this;
         }
 
         public IEnumerable<INdm> GetNdms(ITriangulationOptions triangulationOptions)