* Add backend support for bookmarks
Bookmarks behave like favourites, except they aren't shared with other
users and do not have an associated counter.
* Add spec for bookmark endpoints
* Add front-end support for bookmarks
* Introduce OAuth scopes for bookmarks
* Add bookmarks to archive takeout
* Fix migration
* Coding style fixes
* Fix rebase issue
* Update bookmarked_statuses to latest UI changes
* Update bookmark actions to properly reflect status changes in state
* Add bookmarks item to single-column layout
* Make active bookmarks red
