Add separate property for QML Drag Threshold

Currently the sensitivity of Dragging and Flicking in QML applications is governed by the value of QApplication::startDragDistance. With regard to QWidgets, startDragDistance is used to determine the minimum distance needed to constitute a drag operation. In QML applications this same value to determine the difference between a Touch/Press event and a Drag/Flick gesture in QML. Sharing the same property when an Qt Application could contains both classic QWidgets and QML scenes has the potential to lead to an inconsistent user experience between the two.

Using one property, there is no option to tweak the behavior of one to more closely match the feel of another. Therefore I suggest there be a separate property for adjusting the drag sensitivity in QML.