Evaluate Subject List template/ fix subject nav div id

EDIT: I see this file has already been updated - sorry for the duplicate.  subjects.php: This change allows the code associated with the template for SubjectList to be evaluated, with resulting html displayed, rather than showing the raw php code in the page source. See http://forums.archon.org/viewtopic.php?f=1&t=1373&start=0

subjects-nav.inc.php: fixes insertion of the appropriate div id value.