Expose a biblio_author_id token

Follow-up to #373153: Option to use biblio_authors (token) instead of author/# as the path for authors?: if we want to have nice consistent paths, then it would be great if you could expose another token, like biblio_author_id, so we can alias biblio nodes like /biblio/author/[biblio_author_id]/[title-raw], giving us hackable url's to a (specific ;)) author's other publication's. Will make that another proper feature request.