#4322 CAS: expand output of Sum

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@33898 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#1376 make sure updateCascade only runs if necessary (faster, prevents stack overflow)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@33899 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#4315: should work for unlabeled ineqs too now

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@33901 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e