Make example work with local data

This makes it possible to actually run the example on "local" data stored on dCache at DESY. Without these it tries to fetch data from EOS (and prompts the user for a GRID certificate first).

Still TODO:

• Actually use this repository in the README instead of the one on github.
  • Needs a visibility change to public, otherwise cloning via https doesn't work (@ben.brueers this is probably something only you can do)