cache often used icons


git-svn-id: http://svn.code.sf.net/p/texstudio/code/trunk@4173 92cce386-e96d-4106-809f-596c673a3fd8
Basic annotation support in integrated PDF viewer

git-svn-id: http://svn.code.sf.net/p/texstudio/code/trunk@4174 92cce386-e96d-4106-809f-596c673a3fd8