QmlApp template: Use new 4.7.1 API to enable qml debugging

Qml debugging is now disabled by default, and has to be enabled
explicitly (b2016bbfc9). This has to be done before the
QDView/QDEngine is instantiated ...

The patch introduces a static create method to QmlApplicationViewer,
so that the setup can be hidden from the users main file.

Reviewed-by: Alessandro Portale

share/qtcreator/qml/qmljsdebugger/include/qt_private/qdeclarativedebughelper_p.h

@@ -59,6 +59,10 @@ class QMLJSDEBUGGER_EXTERN QDeclarativeDebugHelper
 public:
     static QScriptEngine *getScriptEngine(QDeclarativeEngine *engine);
     static void setAnimationSlowDownFactor(qreal factor);
+
+    // Enables remote debugging functionality
+    // Only use this for debugging in a safe environment!
+    static void enableDebugging();
 };
 
 QT_END_NAMESPACE