Modify the Impression table to track referrer and status.
Updated view_logger logic to be more flexible in lieu of new use cases incurred by referral addition.  Instead of trying to write subtly different methods for these use cases that can be used cleanly as controller filters, view_logger now implements on method, log_action, which should be called as part of relevant controller actions.  Updated shopping cart controller to create incomplete download actions on update.  This will allow us to track actual referrals for dls, rather than having every dl that occurs through the shopping cart page report that it came from the download queue.
Merge branch 'develop' into track_referrers

Merging in David's shopping cart fix so I can test what I'm doing.
Update cart download job to update preexisting rows, as an initial impression should always be logged when an item is added to the download queue.
Merge branch 'develop' into track_referrers

Merging in David's changes to get the shopping cart show page working.
Fix query in cart_download_job, should actually update the record now.
This test case has been failing forever, and represents kind of an unimportant improvement to the site.  Changing the test.
Require that referrer and status are always set
Update our stubby little impression counting library to at least be functional, update test to the same state.
View logger now accounts for direct access to an object (no referrer) by setting referrer to 'direct'.
Merge pull request #417 from NEU-Libraries/track_referrers

Track referrers