fixes #4548

add excel-export as action

git-svn-id: svn://develop.studip.de/studip/trunk@31283 c5b85792-5220-0410-ad23-ed5b6b8ad999
re #4547 re #4375 check for chdate

git-svn-id: svn://develop.studip.de/studip/trunk@31284 c5b85792-5220-0410-ad23-ed5b6b8ad999