This makes sure that touchEvent() is properly called for all items in
the scene that have an active touch. It does not handle the cancel
event in any other special way.

Change-Id: Id66527ced8cb63d0b29f25f37c139e6d6aec9ba0
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>
Reviewed-by: Martin Jones <martin.jones@nokia.com>