Add Tag class to CallbackManager

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21726 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
more open=>io.open changes, as John advised

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21728 4ae1f11a-8b86-4847-b8af-ab372f36d1fd