Added List::GetArray() and then update Gradient

inc/hgl/type/Gradient.h

@@ -32,7 +32,7 @@ namespace hgl
 
             Comparator<GS> comp;
 
-            hgl::Sort(stop_list,&comp);
+            hgl::Sort(stop_list.GetArray(),&comp);
 
             dirty=false;
         }

inc/hgl/type/List.h

@@ -32,6 +32,9 @@ namespace hgl
 
     public:
 
+            DataArray<T> &      GetArray()          {return data_array;}
+            const DataArray<T> &GetArray()const     {return data_array;}
+
             operator        DataArray<T> & ()       {return data_array;}
             operator const  DataArray<T> & ()const  {return data_array;}