relocate Doxyfile, re #4286

git-svn-id: svn://develop.studip.de/studip/trunk@29902 c5b85792-5220-0410-ad23-ed5b6b8ad999
update Makefile for new Doxygen location, re #4286

git-svn-id: svn://develop.studip.de/studip/trunk@29903 c5b85792-5220-0410-ad23-ed5b6b8ad999