Update Modern theme for MoinMoin wiki.
    
     - Move page trails from heading to page content. This way heading
       will always have a constant height, no matter if page trails are
       active or not.
    
     - Update content of RecentChanges page. Use admonitions in the hint
       section, remove left margin from tables, and remove extra space on
       images and icons showned inside recent changes tables. To show such
       changes, we add RecentChanges.png and RecentChanges.txt files. If
       you want your RecentChanges page to look like this, you need to
       edit the one you have on your wiki and replace its content with
       that in RecentChanges.txt instead.
    
     - Update comments on css and py files.