Show logged-in user's name and avatar atop basement.

Bonus: added parameter assertions when fetching AwfulUser objects.
Remove now-extraneous logging.

Issue is solved, so the logging is no longer needed.
Consolidate scraping and saving in AwfulForumsClient.

* Individual scrapers no longer save the managed object context.
* AwfulForumsClient now handles hiding/showing threads, so we only save once
  after fetching and updating.