Ensure that the prototype chain is checked in property Get

Ensure that the prototype chain is checked in property Get

This commit ensures that the prototype chain is checked during
property Get operations on QObjects and other types in QML by
returning an empty handle from the property Get interceptor if
no valid property with the given name is found.

Task-number: QTBUG-20336
Change-Id: I670ee211c74c0fdcb68c3f91b29fcc0ea8b55d6f
Reviewed-on: http://codereview.qt.nokia.com/1477
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>
Reviewed-by: Kent Hansen <kent.hansen@nokia.com>