Droppable: changing the scope does not update the ddmanager

When changing the scope option of a droppable using droppable("option", "scope", "new"), the droppable will not accept draggables with the correct scope value. This is caused by the fact that the ddmanager is not updated once the scope value changes.

Here is a fiddle showing the bug http://jsfiddle.net/NiGhTTraX/9LwFU/

Expected: After clicking the button, the black draggables can be dropped on the droppables, while the red draggable can't.

Actual: After clicking the button, the black draggables can't be dropped on the droppables, while the red draggable can (this is an indication that the ddmanager still manages the default scope, instead of the new value).

I'll attach my proposed patch in a comment so I can link the ticket number in the pull request.

I had to move some code around to prevent code duplication. I've also included a test in droppable_options.js that replaces the old and unimplemented scope test.