[xcbf] Privacy Objects Draft

I've written the following text for the privacy objects section of
the document. This is a first pass at trying to explain the schema
and encryption processing. Please review and comment to the list
or directly to me if you wish.

I'll be completing a few other sections before I come back to this
part and update the text.

I still plan on posting the final input document to the Baltimore
meeting two weeks before we meet on the ninth of December.

Phil