More clearly show results of folder name translation

For cases like
  http://article.gmane.org/gmane.mail.imap.offlineimap.general/6468
it is beneficial to see that folder name was translated and the result
of this translation on a single line: having log like
{{{
Folder Boring/Wreck [acc: tmarble@info9.net]:
 Syncing Boring/Breck: Gmail -> Maildir
}}}
with translated name on the "Folder" line and original one on the
"Syncing" line isn't very intuitive.

Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>

offlineimap/folder/Base.py

@@ -132,6 +132,13 @@ class BaseFolder(object):
         """The nametrans-transposed name of the folder's name"""
         return self.visiblename
 
+    def getexplainedname(self):
+        """ Name that shows both real and nametrans-mangled values"""
+        if self.name == self.visiblename:
+            return self.name
+        else:
+            return "%s [remote name %s]" % (self.visiblename, self.name)
+
     def getrepository(self):
         """Returns the repository object that this folder is within."""
         return self.repository