b14 - 2013-03-01

Breaking changes:
Major refactoring of both animation and widgets systems as we move to an MVVM-like architecture for user interfaces.
New Animation widget for controlling playback.
AnimationController.js has been deleted.
ClockStep.SYSTEM_CLOCK_DEPENDENT was renamed to ClockStep.SYSTEM_CLOCK_MULTIPLIER
ClockStep.SYSTEM_CLOCK was added to have the clock always match the system time.
ClockRange.LOOP was renamed to ClockRange.LOOP_STOP and now only loops in the forward direction.
Clock.reverseTick was removed, simply negate Clock.multiplier and pass it to Clock.tick.
Clock.shouldAnimate was added to indicate if Clock.tick should actually advance time.
The Timeline widget was moved into the Widgets/Timeline subdirectory.
Dojo/TimelineWidget was removed. You should use the non-toolkit specific Timeline widget directly.
Removed CesiumViewerWidget.fullScreenElement, instead use the CesiumViewerWidget.fullscreen.viewModel.fullScreenElement observable property.
IntersectionTests.rayPlane now takes the new Plane type instead of separate planeNormal and planeD arguments.
Renamed ImageryProviderError to TileProviderError.
Added support for global terrain visualization via CesiumTerrainProvider, ArcGisImageServerTerrainProvider, and VRTheWorldTerrainProvider. See the Terrain Tutorial for more information.
Added FullscreenWidget which is a simple, single-button widget that toggles fullscreen mode of the specified element.
Added interactive extent drawing to the Picking Sandcastle example.
Added HeightmapTessellator to create a mesh from a heightmap.
Added JulianDate.equals
Added Plane for representing the equation of a plane.
Added a line segment-plane intersection test to IntersectionTests.
Improved the lighting used in 2D and Columbus View modes. In general, the surface lighting in these modes should look just like it does in 3D.
Fixed an issue where a PolylineCollection with a model matrix other than the identity would be incorrectly rendered in 2D and Columbus view.
Fixed an issue in the ScreenSpaceCameraController where disabled mouse events can cause the camera to be moved after being re-enabled.