Build value string : correct "function" way to start

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@33940 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Build value string : intersecting lines

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@33941 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Build value string : parallel lines

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@33942 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Build value string : double lines

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@33943 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e