search: Show last added item on top of search stack

Created by: fkling

This reverses the order in which search stack items are rendered so that the most recent item is rendered on top. This only affects the UI. The items are still stored in order so Notebook creation still works as before.

Instead of introducing the id property I could have used the same logic that is used to identify "duplicate" entries (for updating them), but I think that this logic is going away anyway once entries are added manually instead of automatically (in which case the action is deliberate, so no duplicate detection is necessary).