Pass folder names for the foldersort function

Bring the description in the template offlineimap.conf in sync to the
actual implementation: pass folder names to the sorting function, not
the offlineimap.folder.IMAP.IMAPFolder objects themselves.

GitHub issue: https://github.com/OfflineIMAP/offlineimap/issues/27
Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>

offlineimap/repository/IMAP.py

@@ -365,7 +365,7 @@ class IMAPRepository(BaseRepository):
                     def __init__(self, obj, *args):
                         self.obj = obj
                     def __cmp__(self, other):
-                        return mycmp(self.obj, other.obj)
+                        return mycmp(self.obj.getvisiblename(), other.obj.getvisiblename())
                 return K
             retval.sort(key=cmp2key(self.foldersort))