Move drag-and-drop code to separate file
(to improve startup performance)
(#11)
Move readFromClipboard() to utils.js
(to improve startup performance)
Sync readFromClipboard() with code from Firefox 30.0a1 (2014-03-08)
Don't override "status" argument
Drag-and-drop: ignore, if dataTransfer is missing (Firefox < 3.5)
(#11)