Merge remote-tracking branch 'remotes/upstream/master'

* remotes/upstream/master:
  parse_url: Fixed a problem in the detection if there was an image or not. Additionally removed some test content.
  rev update
  Changed markdown to enable diaspora postings with images that contain links
  bbcode: two new bbcode elements (style, class) for CSS
  Moving the index creation commands into a readme file due to the fact that creating of these indexes is really slow.
  network: Caching of images
  scale_external_images: Fix: Hadn't looked for pictures in the format [img=XxY]
  Further performance improvements
  Speed improvements in the database