Move to a cipher suite blacklist (WIP)

This is based on the long set of negotiated changes added to #615.  This adds the blacklist as Sam Hartman proposed at IETF 91.

Closes #612.
Based on the definition in RFC 2119, "MAY" cannot be used for anything which would produce a complete interop failure; only reduced functionality. "SHOULD" needs to be used for this and any other INADEQUATE_SECURITY error, at minimum.

http://tools.ietf.org/html/rfc2119

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5. MAY  This word, or the adjective "OPTIONAL", mean that an item is
   truly optional.  One vendor may choose to include the item because a
   particular marketplace requires it or because the vendor feels that
   it enhances the product while another vendor may omit the same item.
   An implementation which does not include a particular option MUST be
   prepared to interoperate with another implementation which does
   include the option, though perhaps with reduced functionality. In the
   same vein an implementation which does include a particular option
   MUST be prepared to interoperate with another implementation which
   does not include the option (except, of course, for the feature the
   option provides.)
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An implementation MUST be prepared to interoperate with another that does not concur, which is not possible if one errors with INADEQUATE_SECURITY.

(also posted to list, but moderation queue is slow)