Add a new password validator that determines whether a proposed new password
is acceptable based on how similar it is to the user's current password.  The
processing uses the Levenshtein Distance algorithm to determine the number of
changes required to convert the current password into the new password (a
change may be either inserting a new character, removing an existing character,
or replacing an existing character).

Contributed By:  Ales Novak
OpenDS Issue Number:  340