Cosmetics: acknowledging Heidelberg in the PN Footer

[samosafuz]

I noticed that the PE footer includes Heidelberg in its list of Produced by:

(this is controlled by sosol/app/views/cross_site/_footer.html.erb)

        <p>Produced by</p>
        <p><a href="http://blogs.library.duke.edu/dcthree/">The Duke Collaboratory for Classics Computing</a> 
          <br/>&amp; the <a href="http://www.nyu.edu/isaw/">Institute for the Study of the Ancient World</a> 
          <br/>&amp; the <a href="http://www.uni-heidelberg.de/fakultaeten/philosophie/zaw/papy/">Institute of Papyrology Heidelberg</a>
        </p>

But the same is not true across PN. I've therefore added the relevant line of html to the various files in papyri/navigator/pn-site where it is missing, on the assumption that its omission is simply an oversight.

[samosafuz]

Closing due to discrete commits added to single PR.