Dn class cleanup and doco : done

[Emmanuel Lecharny]

Hi guys,

I just finished to cleanup the Dn class, and the Dn documentation page.
Please review the following page : 
https://cwiki.apache.org/confluence/display/DIRAPI/Dn

Comments welcomed !

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Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com