Keeping style names for generated paragraphs

[Frédéric Péters]

It would be nice if such an odt snippet:

  <text:p text:style-name="Example">
    <office:annotation>
       <text:p>do text if blah()</text:p>
       <text:p>from xhtml(foo.bar)</text:p>
    </office:annotation>
    bla bla bla
  </text:p>

when passed through appy.pod.renderer, yielded text paragraphs (containing foo.bar) with the given style (here "Example"), instead of an attribute-less <text:p>.

The attached patch (created on top of revision 10) does it in a rough way that is certainly not proper for inclusion, I'd be happy if a generic solution could be found.