WIP: reduce number of mails per day, from currently 34 down to 32 - see #912591

  - master-bin/detect_archive_issues: redirect logs to htdocs/logs to spare
    us two mails per day.
  - lib/write_log.sh: new helper to publish logs in htdocs/logs.

Signed-off-by: Holger Levsen <holger@layer-acht.org>