ticket 1569 - Test DN object non-latin Unicode support
    
    The DN unittest was lacking a test for i18n. The unittest was
    updated to store "Hello" in Arabic with both utf-8 and unicode
    and verify the values could be properly retrieved and converted
    to dn string syntax.
    
    During the testing a few problems were discovered and corrected.
    
    * passing in utf-8 caused an ASCII decode error becuase of Python's
      silly default encoding of ASCII. The fix was to explictly use
      the utf-8 codec.
    
    * there were a couple of places where encode/decode were not
      called correctly.
    
    * the internal attr and value members of the AVA class were renamed
      to explicitly show they are stored as unicode.
    
    Of course the unittest was updated as well.