LP#1674364 - Use database bib id for cover art lookup

LP#1674364 - Use database bib id for cover art lookup

Export the 901c as the URN:BIBID identifier to allow the
ATOM2XHTML.xsl to construct a cover art img link using it.

Testing Notes:

I used a bookbag to test this out.
1. Create a public bookbag of items and grab the bookbag id.
2. View the source of these links on your system to see the current output.
 /opac/extras/feed/bookbag/atom/<bookbagid>
 /opac/extras/feed/bookbag/html-full/<bookbagid>
   Make note that the jacket img link uses the ISBN to lookup cover art.

Make changes.
1. Restart supercat to re-load xsl transfor files.
  osrf_control -l --service open-ils.supercat --restart
2. View the source and output of these links on your system to see the changes.
 /opac/extras/feed/bookbag/atom/<bookbagid>
 /opac/extras/feed/bookbag/html-full/<bookbagid>
   The cover art images should show up now in the html-full, and the
   URN:BIBID: identifier should be populated in the atom file.

Signed-off-by: Josh Stompro <stompro@stompro.org>