cronjobs: add unit 'seconds' to log display, re #2793

git-svn-id: svn://develop.studip.de/studip/trunk@25444 c5b85792-5220-0410-ad23-ed5b6b8ad999
generate valid class name, fixes #3241, re #812

git-svn-id: svn://develop.studip.de/studip/trunk@25445 c5b85792-5220-0410-ad23-ed5b6b8ad999