Report a vetoable property update to any registered listeners. If anyone vetos the change, then fire a new event reverting everyone to the old value and then rethrow the PropertyVetoException.
No event is fired if old and new are equal and non-null.
@param name The programmatic name of the property that is about tochange
@param oldValue The old value of the property
@param newValue - The new value of the property
@throws PropertyVetoException if the recipient wishes the propertychange to be rolled back.