new module to enable editing and deleting of bookmarks
Add a new module, bookmark, which enables the editing and deleting of
bookmarks. The interactive bookmark function, which formerly always
added a new bookmark, is replaced by a new function which adds a
bookmark only if no bookmark for the current URI already exists. If a
bookmark exists, the user is given the option of editing its title,
running an interactive function (via a key binding) to delete it, or
running another function to edit the bookmark's URI.