moc: Move the property access code to the qt_static_metacall

That way we will be able to access property of objects that are not QObject
(Q_GADGET)

Change-Id: Ib8ef6e52fc621e0b0d6530f82b1aa205f1ed5fd9
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>