GraphicElements are no longer supported in DataGroup. This allowed us to clean up a lot of the code (hurray!)
Moreover, there are some other cleanups. We now support null items. Item renderers are strongly typed as IVisualElements now (an item renderer must be an IVisualElement and a DisplayObject). We also don't dispatch events when changing the itemRenderer or itemRendererFunction anymore as there's no need to do it and no need to make these properties bindable.
Also a minor fix in FlexNativeMenu where the binding metadata was using the wrong event.
QE Notes: Steve's already changed mustella tests for me.
Doc Notes: None
Bugs: SDK-18040, SDK-18046, SDK-18045
tests: checkintests, mustella DataGroup, FxDataContainer, FxList, Group