QtQuick.Dialogs: check for inheriting from QApplication

Widget-based dialogs are allowed if the application is a
QApplication, but subclassing is OK too.

Task-number: QTBUG-35769
Change-Id: Iec329792d7c1d85adcb1c3542444f0e92792b20b
Reviewed-by: Liang Qi <liang.qi@digia.com>
QtQuick ColorDialog: ensure slider rotation takes effect

Task-number: QTBUG-35206
Change-Id: Ia6b4f743cd9bea937eb891ddd16776f975d42bcd
Reviewed-by: Jan Arve Sæther <jan-arve.saether@digia.com>
Doc: Fix broken links

Change-Id: I4c4577edde96978a986606bf30fbb925f871bd42
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>