Add polygon shape

StructureHelperLogics/NdmCalculations/Primitives/NamedAreaPoint.cs

@@ -11,7 +11,7 @@ namespace StructureHelperLogics.NdmCalculations.Primitives
     public class NamedAreaPoint : INamedAreaPoint
     {
         public string Name { get; set; }
-        public Point2D Point { get; set; }
+        public IPoint2D Point { get; set; }
         public double Area { get; set; }
     }
 }