Changed search for a droppable

I changed the method used to find by a draggable item to find a droppable. 

The important part is that a element that is visible to the mouse will now block the search for more droppables on siblings (and siblings of the parents). The main reason for me to apply to change is to offer a way to block the search for droppables by other objects. For example if a window is on the screen and on a different layer, behind the window there is a droppable, the expected way for the whole thing to work is that the droppable is not accessible. So dropping a draggable on the window "over" the droppable will not drop the draggable on the droppable.

How ever I am not sure what other side effects this might have. It shouldn't have any, but please tell me if anything comes to mind.