Slapos'ify config updates brought by sync with omnibus-gitlab (see merge
in the previous patch). Changes:

- default visibility levels gone away (see merge commit and
  https://gitlab.com/gitlab-org/omnibus-gitlab/commit/b5ebbab3 )

- there are new settings for GitLab Pages and Elasticsearch, which are EE
  only and thus we do not support them.

- there are new settings for auxiliary cron-like jobs, which we do not
  support for now, since they are used either for CI (not supported by
  us) or EE features.

Configuration files that were synced, but did not changed are also
marked as updated, so it is easier to track their changes to upstream in
the future.

/cc @kazuhiko, @jerome