Attempt to appease the XML gods

The new xml2rfc version 2 doesn't give us the option of "fast"
syntax checking, so we can't sneak by any more.  Attempt to clean up:

<artwork> lives within <figure>
<figure> and <list> live within <t>
<reference> needs a <date>

Change-Id: I95e8ead5ec43b6d69de87a461cacfb20c04ab273
Let 'xmllint --format' run its course

Since we just mucked around with the structure a bunch.

Change-Id: I2950171cd637d2dfd97538cd393a44e68691ea77