XSD update

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@22840 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Tests for XML

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@22841 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e