SceneObject: fix groups() and ids() implementation
Merge pull request #4 from roguenet/updateModeTransition-memory

Save on per-frame memory allocation.
unused import
ImageResource.require()
PointerAdapter.withTouchId -> Input.newPointerListener
Input.newTouchListener, newKeyboardListener
MovieButton. I coulda sworn I'd already written this.
GridLayoutSprite
fixes
Dragging overhaul

- DragHandler interface
- Input has a builder interface for creating callback-based DragHandlers
- Dragger moved to the input package