new web text editor buttons, using img tag  

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29680 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
web tooltip tweaks

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29681 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e