added DragAdornerTemplateSelector

In my application there are different types of objects that might be dragged, thus I can not use a fixed `DragAdornerTemplate`. Therefore I added a new property `DragAdornerTemplateSelector` of type `DataTemplateSelector`.

I added an additional tab to the demo application: If you drag items on that page from the left to the right, even numbers are blue and odd numbers are green.

A new drop on NuGet would be appreciated :blush: