Fix for data URL thumbnails

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36083 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Avoid sending outdated token

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36084 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
tooltips (web): link to wiki-page

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36085 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
attach/detach (related to #4506 and #4481)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36086 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e