z-index set to 1000 when an element is dragged

I’m using jQuery++ to make an element with a high z-index draggable. Unfortunately, [this line of code](https://github.com/bitovi/jquerypp/blob/85a2d54d2e59f9e511469a9223609412fc16d60e/event/drag/core/core.js#L268) sets the `z-index` to `1000`, causing my element to go under other elements while being dragged.
