QtIFW

Fix regression after porting to QJSEngine.

Setting a dynamic property of a dynamic page from JS doesn't have
any effect anymore, as the properties are not synced. Now we define
the property directly on the JavaScript object and connect it to
corresponding C++ page with static Qt properties.

Task-number: QTIFW-562
Change-Id: If95222a94ebee7f8bb455792eab96c5e9bc19b86
Reviewed-by: Niels Weber <niels.weber@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>