Fixed various inconsistencies with deleting properties, added wxPGProperty::DeleteChildren()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57442 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/propgrid/property.h

@@ -907,6 +907,11 @@ public:
     */
     bool AreChildrenComponents() const;
 
+    /**
+        Deletes children of the property.
+    */
+    void DeleteChildren();
+
     /**
         Removes entry from property's wxPGChoices and editor control (if it is active).