Extent camera flight

CameraFlightPath:
* Added `createAnimationExtent` and added specs
* Cleaned up some allocations
* Fixed issue for camera flight paths in case of `mode === SceneMode.MORPHING`

CameraController:
* Added `getExtentCameraCoordinates` and added specs
* Modified view extent functions to work with both `viewExtent` and `getExtentCameraCoordinates`

Updated Sandcastle example.