Enable native undo/redo

[michael]

Until there's an API for creating native history entries (michael/web-editing#1), I may reside to a hack that Johannes Wilm made me aware of.

When a Svedit editor gets focus for the first time, two fake history entries (via document.execCommand) could be created, followed by by a document.execCommand('undo'). Now the native undo and redo action becomes available and we can handle historyUndo and historyRedo events at

This would activate "shake to undo/redo" on iphones (and double finger swipe left/right on android) for instance.