Create an 'Enabled' property for QDeclarativeItem

It would be useful to have a property on Items which disables user input on the entire sub-tree. This should probably go along with an effect which indicates this to the user, such as blending with a dark color, or hooks to make providing such an effect easy.

See QTBUG-15797 for further details. That task is rejected because that aspect of QGraphicsObject is tied too heavily to the scene implementation, but the concept is worth exploring later in a less implementation-dependent manner.