Description

this patch allows passing a function as the containment of the droppable. the function should return an array of elements... it is backward compatible, and will work with passing an array as before.

i needed this because i had droppable elements with many items in them, and they were being dynamically added and removed from the page, so doing everytime Sortable.create() was just too sluggish... using the function technique though, i kept an array of the elements currently in the container, and the function returned them to the droppable as required...