DPDD references a TRAC document

DPDD includes a URL to http://ls.st/l9u which end up going to a TRAC page talking about the Winter 2013 LSST DM Data Challenge Release Notes.

Given the current status of TRAC I don't think LSE documents should point to those URLs. Can we please consider moving this content somewhere else. I'm not entirely sure whether it should be a DM tech note or a confluence page (I'd say an LDM but it's not clear people like nicely formatted PDFs entering an archive).