internationalization (setLabels() for saveBeforeOpen-Dialog); enhance functionality of goBack()

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@26787 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
add cordova

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@26788 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Worksheet GUI plugged in

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@26789 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e