server: fix inverse URL redirection for root path + allow multiple inverse redirections: - inverse redirection is now working for root path - a list can now be used in `url_redirections_dict`: the first item only will be used for redirection, but all items will be used for inverse redirection. e.g.: if in `url_redirections_dict` we have `"/": ["/u/some_user/blog", "/blog/view/some_user_jid@example.org"]`, root will redirect to "/u/some_user/blog", but both "/u/some_user/blog" and "/blog/view/some_user_jid@example.org" will have an inverse redirection to the root path fix 395