Add an option to enable reporting in the UI

Mostly for #1777, but also probably good to open it up.

Actually, I'd rather change "default" to mean enabled, and have this as the way to turn it off.  I can do that instead if you think it's fine, or we can do that later or not at all depending.

Wording's not perfect but it never is... I intend for this same config setting to be used for submitting compatibility ratings/screenshots/whatever too.

-[Unknown]