gedit, libmediaart, fix xdg-user-dirs, enable GI in grilo, prioritize nautilus mimetype, seahorse, gnome-music, glade, gnome-documents

The baobab mimetype removal is a temporarily hack. A better solution would be to create a gnome-mimeapps.list as described here: http://standards.freedesktop.org/mime-apps-spec/mime-apps-spec-latest.html . I'm going to work on it in this PR.
Also move some packages to the right gnome3 subdir.