New autocomplete UI

This includes:

* The new autocomplete dialog UI
* If there are too many autocomplete results, you can scroll through them
* Selecting results with key up/down will make sure the selected item is scrolled into view
* The getFiltered function now includes caching and a debouncer (to make sure we don't trigger too many requests one after the other - eg. when typing in the search box)
* When closing the dialog the focus will go back to the email editor
* Change the SQL search for quicktexts to use `LIKE` for `shortcut`, as for `title` and `body`