moved the code to render the various formats of the list of bookmarks from and if statement in BookmarkController::list() to a set of as_$format() methods in BookmarksList
moved the _get_list_links() method from BookmarkController to BookmarksList
Bookmarks::get_bookmarks() returns a BookmarksList instead of an array
the ?format parameter accepts "atom" to render arbitrary sets of results as Atom feeds; the BookmarkController::feed() method just calls as_atom() on a BookmarksList search result object