expose pref to show notifications even when trusted cert fails

[danwent]

Let users opt to get strong warnings if the notary results are inconsistent, even for certificates trusted by the browser.

Email from user:

Would you consider including some sort of obvious notification when Perspectives throws an error? I was on a google.com site the other day, and I browsed around to several pages before I noticed that Perspectives had turn red. I had the security turned to High, and it appeared that Google had deployed a fresh certificate of some sort (the notary servers agreed, but the quorum duration was not met). It would be very good to be alerted immediately, instead of having to randomly notice.

[ghost]

Should this really be an option or not simply the default behaviour?