Have log subscribers subscribe to the actual events, so the subscriber doesn't subscribe to *every* event, so we can have events that are slow-ish but are not actually run in production.

Optimize AS::Notifications to remember which subscribers don't match and not run them. This will allow notifications that are only useful in dev or testing to run efficiently in production.

Change AV formats so they can delegate to the controller. Now users (or plugins) can override details_for_render in their controllers and add appropriate additional details. Now if only they could *do* something with those details...

[#3891 state:committed]
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

Signed-off-by: NJosé Valim <jose.valim@gmail.com>