Draft: WidgetExplorer delegate: Port away from KDeclarative DragArea
This ports the widget explorer away from DragArea, instead using a combination of Control, Drag and Handlers to achieve the same result, while giving more control to the QML code over which behaviours are desired. Most prominently, we can now differentiate behaviour between mouse and touch input, with touch input activating a drag on horizontal movement, leaving vertical movement for scrolling.
Draft because the drag on touch doesn't seem to work properly, it starts the drag but doesn't seem to update it after that.