Using a well-known user agent in curl.
Making the cache accessible to the outside world.

  The URL looks like http://openspace.slopjong.de/cache/syn2cat
  and the last part of the URL is the space name as seen in the
  directory.json file. Special characters must be urlencoded.
Using a second 'public' directory with cached URLs mixed.

   Some spaces want reduce the traffic why a cache has been introduced.
   Now it's necessary to keep two directories, one private with the
   original space URLs and one public which contains URLs to the
   OpenSpaceLint cache. When a space is added it's added to both.
   Later, not yet in this commit, the cache/schedule field will be
   considered to decide whether to insert the cache URL to the public
   directory.
Added a fake space for testing purpose.