Added wxPropertyGrid::SetUnspecifiedValueAppearance(); Added wxPGEditor::SetControlAppearance() for applying wxPGCell attributes on a property editor.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62973 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/propgrid/property.h

@@ -254,6 +254,11 @@ public:
         return (m_refData && GetData()->m_hasValidText);
     }
 
+    /**
+        Sets empty but valid data to this cell object.
+    */
+    void SetEmptyData();
+
     /**
         Merges valid data from srcCell into this.
     */