Allow video hiding while controller is visible for audio only


There could be activities that either have audio only or want to hide the video/animation and hear only the audio

A split pane could exist in the player to separate the video area and the controller.

That way either the video or the controller could get hidden or both could be visible (as now). In case the video is hidden the control should change height (that is the video controller should have a max height constraint that doesn't stop the splitpane from resizing but causes the whole splitpane to resize itself)

Also see issue "Video controller hiding" (http://lvs.codeplex.com/workitem/11510)