doubleClick-handling in the AlgebraView

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@26888 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
(Worksheet) use title of ggT if title of XML is empty

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@26889 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e