refs #2878 : add bigger mail icon

git-svn-id: svn://develop.studip.de/studip/trunk@25629 c5b85792-5220-0410-ad23-ed5b6b8ad999
refs #2878 : accept instead of decline

git-svn-id: svn://develop.studip.de/studip/trunk@25630 c5b85792-5220-0410-ad23-ed5b6b8ad999