Splits the transitions into their own files, which will make it possible to blacklist/whitelist them.
Improves the bounce transitions.
Adds the spring transition.
Adds deprecation developer warning to SC.SceneView.
Removes unneeded code.
Publicizes _state as currentState, privatizes isRendered as _isRendered and adds Enum for current view states.
Changes SC.SheetPane to use transition plugins:  17 lines added, 56 lines removed!