QRotationSensor should provide Quaternion

Currently QRotationSensor provides a QRotationReading which contains the Euler Angles of the orientation of the device. Euler angles are known to have problems with some singularity points in space (such as when looking straight down the yaw is undefined). This can easily be solved by providing a Quaternion representation from the Sensors. Both iOS and Android provide a quaternion so it should not be difficult to pass this to Qt.

This is important for any Virtual/Augmented Reality application.