Add tracking code (bug 874076)

Not implemented (yet?):
7. We don't have purchase data, probably should happen in webpay
9. Waiting on info in bug (login actions)
36. We don't have a language setting, and GA already collects navigator.language (which we use to determine language)

Notes:
33. We pass the app slug rather than name/ID because we don't have the name or ID in this view, particularly if the user is deep-linked.
35. I made this happen on any listing page (search, cat, featured, purchases), rather than just search or categories (the doc doesn't differentiate).

https://docs.google.com/spreadsheet/ccc?key=0AqvoOaUZL-jwdDNnZ3Z1X1FFbWhFRHhZdEFSY0dLcVE#gid=5

cc @clouserw