plugins XEP-0060, XEP-0277, groupblog: comments implementation (first draft, not finished yet): - PubSub options constants are moved to XEP-0060 - comments url are generated/parsed according to XEP-0277 - microblog data can now have the following keys: - "comments", with the url as given in the <link> tag - "comments_service", with the jid of the PubSub service hosting the comments - "comments_node", with the parsed node - comments nodes use different access_model according to parent microblog item access - publisher is not verified yet, see FIXME warning - so far, comments node are automatically subscribed - some bug fixes