Widgets: 
- Don't deactivate "draggable" on the widget when the chooser is open. Makes it possible to still drag the "widget-in-question".
- Change the chooser's HTML id to a class to avoid collisions when cloning.
- Refresh the "sortable" positions when an open widget is dragged. Fixes problems moving the widget up or down in the same sidebar.
See #25821

git-svn-id: https://develop.svn.wordpress.org/trunk@26366 602fd350-edb4-49c9-b593-d223f7449a82