#3784 almost working!

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29759 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
rename Roboto -> GeogebraSans-Regular / GeogebraSerif-Regular and correct problem with &radic; in Serif

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29760 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Ticket #3735: enabling sans-serif again (with as little change as possible), before testing and enabling other features again

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29761 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e