Ticket #2971: start fixing the spreadsheet bugs

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23049 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Ticket #2971: continue fixing the bugs in spreadsheet view

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23050 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e