refs #2758 : fixes wrong isset on virtual value

git-svn-id: svn://develop.studip.de/studip/trunk@25349 c5b85792-5220-0410-ad23-ed5b6b8ad999
correct classname to DbSnapshot, refs #812

git-svn-id: svn://develop.studip.de/studip/trunk@25350 c5b85792-5220-0410-ad23-ed5b6b8ad999
autoload class Request, refs #812

git-svn-id: svn://develop.studip.de/studip/trunk@25351 c5b85792-5220-0410-ad23-ed5b6b8ad999