Add ability to return IDN encoded bare addresses.

[mms] Added the 'bare_address_idn' property to Horde_Mail_Rfc822_Address.
[mms] Added the 'bare_addresses_idn' property to Horde_Mail_Rfc822_List.
phpdoc
[mms] Ensure Registry exists in error handler before attempting to access it (Bug #12540).
[mms] Translate mailbox names from UTF7-IMAP -> UTF-8 in return from Horde_Imap_Client_Base#getMetadata() (Bug #12541).