Add Tag class to CallbackManager

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/trunk@21727 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/trunk@21729 4ae1f11a-8b86-4847-b8af-ab372f36d1fd