Drag-moving text unlinks citations

[adomasven]

Might be able to inject into the drop event handler and do the same as we do for cuts

[adomasven]

The GDocs editor implements custom text drag handlers when dragging within document. I tried hooking into the custom event doctext-drag-drop which I managed to track down being used in the minified code, but it doesn't seem to be fired on the DOM. The gdocs editor code is minified beyond further investigability(?), so I don't think we can actually address this. Better notifications for unlinked citations is all we have in this regard.

Keeping the issue open in case things appear to change on gdocs side and it becomes worthy of reinvestigation.