plugin groupblog, XEP-0071, XEP-0277, text_syntaxes: manage raw/rich/xhtml data for content/title: Implementation should follow the following formal specification: "title" and "content" data can be passed in raw, xhtml or rich format. When we receive from a frontend a new/updated microblog item: - keys "title" or "content" have to be escaped (disable HTML tags) - keys "title_rich" or "content_rich" have to be converted from the current syntax to XHTML - keys "title_xhtml" or "content_xhtml" have to be cleaned from unwanted XHTML content Rules to deal with concurrent keys: - existence of both "*_xhtml" and "*_rich" keys must raise an exception - existence of both raw and ("*_xhtml" or "*_rich") is OK As the storage always need raw data, if it is not given by the user it can be extracted from the "*_rich" or "*_xhtml" data (remove the XHTML tags). When a frontend wants to edit a blog post that contains XHTML title or content, the conversion is made from XHTML to the current user-defined syntax. - plugin text_syntaxes: added "text" syntax (using lxml)