inst_members, inst_admin links to trails, re #3768

git-svn-id: svn://develop.studip.de/studip/trunk@31232 c5b85792-5220-0410-ad23-ed5b6b8ad999
fixes #4532

git-svn-id: svn://develop.studip.de/studip/trunk@31233 c5b85792-5220-0410-ad23-ed5b6b8ad999