Set up the CSS to convert to PDF using Prince XML.

* Finished out the margin boxes to put the document number and current section
  in the right corners.
* Adjusted font sizes and spacing to better match the C++ standard.
* Switched to using <h1> to define section titles and <header> to style them,
  for better control over PDF bookmarks.
* Generated page numbers in the table of contents when printing.
* Lined up the markers better in the table of contents.
* Changed how styles are transferred to the standalone document, so that styles
  the browser doesn't understand are preserved.
* Fixed some formatting in the Normative References section.
Rename the HTML files, and check in the Prince-generated PDF.