Added DragAndDrop example scene
Added Clickable2D and Draggable2D components to make sprites clickable
and draggable.
Added event handlers which list for events from the Clickable2D and
Draggable2D components.
Can set the ‘Execute On Event’ property to define when a sequence
starts executing.
Added a ‘Start Game’ event handler.
Removed old system of specifying a start sequence on the Fungus Script.