World.destroy incorrectly clashed with the Group.destroy method it over-rode, renamed to World.shutdown and updated StateManager accordingly.
World.shutdown now removes all children iteratively, calling destroy on each one, ultimately performing a soft reset of the World.
Objects with a scale.x or y of 0 are no longer considered valid for input (fix #602)
InputHandler will set the browser pointer back to default if destroyed while over (fix #602)
Group.destroy has a new parameter: `soft`. A soft destruction won't remove the Group from its parent or null game references. Default is `false`.
InputHandler.validForInput is a new method that checks if the handler and its owner should be considered for Pointer input handling or not.
Group.replace will now return the old child, the one that was replaced in the Group.