Fix qdoc warnings, do some editing and cross-link between
QQuickWidget and QQuickView class references.

Task-number: QTBUG-37272
Change-Id: I48d3a01e7c6315be329e24a5c5f7635697629316
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>