PathView increment/decrementCurrentIndex behavior depends on highlightMoveDuration property

PathView's increment/decrementCurrentIndex methods depend on the hightlightMoveDuration setting. Basically the index will only change if the current pathview animation is complete. So if you call these repeatedly at a high frequency, the index you end up at is somewhat undefined.

So the method names are misleading the way they are currently implemented.

If you try the spinner example that comes with Qt 5.1.1 (in examples/quick/ui-components/spinner), you'll find that if you try to hold a cursor key down (up or down), the PathView item does not handle that properly. Scrolling slows down every time it received a new keyboard event, so it's not usable in a real-world application.

In comparison with Quick 1.0: the same spinner example there is somewhat better. Current index is incremented properly, but the animation is jerky.