[giac] improved output form of Solve/CSolve/Integral

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25019 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[giac] Updated unit tests

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25020 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e