DOC: add information on where to report vulnerabilities + pointer to HOWTO_Seek_Help

originally following command was used to add header to all config files:

  sed -ie '/# Author/ i\# Please report vulnerabilities to fail2ban-vulnerabilities at lists dot sourceforge dot net\n# and see http://www.fail2ban.org/wiki/index.php/HOWTO_Seek_Help for generic bug-reports.\n#' action.d/* filter.d/*

but it would be overkill ATM causing havoc in user-tuned configs -- postponed for now

Also adjusted the release date for today (by mistake in 1 commit ... sorry)