Already done:
http://www.fast-downward.org/TranslatorOutputFormat
http://www.fast-downward.org/PreprocessorOutputFormat

For src/dist and other cleanup targets, see issue151.

We should add proper documentation about the output file formats of the
translator and preprocessor to the wiki. Right now, the information lives in the
repository under src/dist/data/doc, but it should be in the wiki instead.

Note that the current description is not fully up to date:

 * it misses the action cost info ("begin_metric"/"end_metric",
   cost fields for operators)

 * it doesn't reflect the fact that "<none of those>" fields are no longer
   always generated (or rather, they are, but sometimes they are pruned by
   the translator before generating the output)

 * The information on "all.groups" and when it is/isn't needed is a bit
   sketchy (but not wrong a such).

The complete src/dist directory is legacy stuff from pre-Mercurial times. We
should get rid of it eventually.