This update addresses nesting of Assets, specifically the new AssetViews. This required a wholesale refactoring of FlexItems, because nested views were getting created (instantiated) well in advance of actually being associated with a MovieClip, and FlexItems need to know the clip before they can do their magic.
FlexItems can now defer their update cycle until the AssetView gets its clip.
Adding a nested AssetView to a "parent" AssetView is the same as adding a ScreenAssetView to a ScreenView: addAsset(). This ensures that the child asset is registered with the parent, and allows the parent to bubble up activate(), deactivate(), localize(), setupBeforeLocalize() and setupAfterLocalize(), among others.