cancelCommand: missing confirmation prompt for new and shadow tiddlers

[FND]

When canceling during editing, a confirmation prompt currently only appears when the respective tiddler already exists in the store. When editing a new tiddler or a shadow tiddler, there is no confirmation prompt - which is inconsistent and potentially harmful.

The attached patch thus makes the confirmation prompt when one of the following conditions is met:

• is existing tiddler and has changes
• is new tiddler (tiddler not in store)
• is shadow tiddler

Drawback: Closing new tiddlers or shadow tiddlers will result in a confirmation prompt even if nothing has been altered there.

[FND]

This should be solved by checking for shadow tiddlers in Story.prototype.hasChanges, making sure that the tiddler text is different from the default shadow value.

[FND]

Fixed in changeset:10122.