sidebar: refine icon handling for list items by changing from list style images to background images, re #3768

git-svn-id: svn://develop.studip.de/studip/trunk@30702 c5b85792-5220-0410-ad23-ed5b6b8ad999
sidebar: refine icon handling for list items by changing from list style images to background images, re #3768

git-svn-id: svn://develop.studip.de/studip/trunk@30703 c5b85792-5220-0410-ad23-ed5b6b8ad999