Rendering of UIP sub-presentations in the edit view

Implement rendering of the UIP 3D sub-presentations in the edit view, so that user can see the 3D the sub-presentations while they edit the 3D content. In this initial implementation most important is to get the content visible.

Second priority is to have some animation playback also working, even if the timelines are not synchronised in any way to the 3D rendering at this stage.

Optional target is to have the animation follow the "master" UIP timeline scrubbing in the sub-presentations.