only one material can be selected in browseGUI;
open material if it's selected and clicked again

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28233 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
remove "sharedBy", use another date-format

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28234 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e