Re-implemented DynamicGrid.ConfigureColumns

inabox.wpf/DynamicGrid/DynamicGrid.cs

@@ -943,11 +943,18 @@ public abstract class DynamicGrid<T> : DynamicGrid, IDynamicGridUIComponentParen
     protected virtual void ConfigureColumnGroups()
     {
     }
+
+    protected virtual void ConfigureColumns(DynamicGridColumns columns)
+    {
+    }
     
     private void ReloadColumns()
     {
-        VisibleColumns = LoadColumns();
+        ConfigureColumns(MasterColumns);
 
+        VisibleColumns = LoadColumns();
+        ConfigureColumns(VisibleColumns);
+        
         ColumnGroupings.Clear();
         ConfigureColumnGroups();