Dynamically load/unload per request

[jmoses]

It would be great if you could enable query_reviewer for a single request. Mostly so you can profile a particular page once, in production mode, but not have the overhead of leaving it on for all requests. It almost looks like you could do that by overriding how enabled? works, but it loads a bunch of modules, and I don't think there's an easy way to unload them after the request is completed.

If I can get good direction on this, it'd probably be worth my time to fork and pull.