Bug 1068888 - [Rocketbar] Debounce place saving until timeout or apploaded

https://bugzilla.mozilla.org/show_bug.cgi?id=1068888
For both the title and the icon change, we shouldnt lose data if we dont have a locally cached object, editPlace will delete that object and we can receive these events at any time so I think this should |this._placeChanges[url] = this._placeChanges[url] || this.defaultPlace();| (or this._placeChanges[url] = this._placeChanges[url] || {};) if it makes merging easer, downstream should always be checking for any fields it expects