Separate PaneView:

This separation should make it easier to work
on the individual components, such as animation of panes,
or card life cycle, while minimizing interference.

The new entities:
- CardView: manages the dom lifecycle of the card sandbox (iframe)
- PaneView: manages the container wrapping the cardView
- PaneController: decorates the pane, and provides a place to store the card and isHidden
- PanesController: is only needed because "render" with a record array as its context doesn't appear to generate the correct controller type.