OSMF SVN

Remainder of fix for FM-383: Ensure that when SerialElement (via TraitLoader) attempts to load the next playable child (on child transitions), it takes into account the possibility that the LoadTrait of a child that it's loading will be replaced by another LoadTrait (which would then become the one it needs to load). Also updated the CaptioningProxyElement to use a higher listener priority so that it ensures that the SerialElement doesn't think that the load is complete when transitioning from child to child. (This is a necessary step for clients who use the swapping LoadTrait trick, but there might be a more robust approach to the same problem.)

Partial fix for FM-383: ProxyElement needs to dispatch traitRemove/traitAdd event pairs when the proxy adds or removes a trait that also exists on the proxied element.

Sync with latest layout API changes.

PARB feedback: rename LayoutProperties to LayoutRendererProperties.

PARB feedback: rename LayoutRenderer to LayoutRendererBase, rename DefaultLayoutRenderer to LayoutRenderer.

Updating source path to control bar plugin.

Moving ControlBarPluginSample and Test into the plug-ins folder.

PARB feedback: taking out 'media' references; renaming measureMedia to measure, and updateMediaDisplay to layout.

PARB feedback: updating sample to use measureWidth and height.

PARB feedback: renaming LayoutRenderer.targets to hasTarget.