Add extended apikey stats

This adds new stat counters to track if we responded with the best possible position estimate given the incoming request data. We only want to enable this one some of the api keys, like those used for actual Firefox OS devices.

The changes are done in two parts, one commit to clean up test failures based on us doing wifi data validation earlier in the chain. The other implementing the actual additional stats. And I also snuck in the missing metric docs for the new Redis update queues and removed some long repetitive lists from the same docs.

@jaredkerim f?
The problem is that this happens in the check_api_key decorator and there's no good way to pass return values from that one to the underlying function scope. Piggy backing on the request was the least evil I could think of. And I made sure to get those values away from the request inside the view handler, so the underlying search_all_sources function continues to work without a request object. The view handler itself already is all about dealing with a request object, so I think making testing harder isn't a concern in this specific case.