[Enigmail] Setting trust levels for unknown keys

[Robert J. Hansen]

Allen Schultz wrote:
> Or better yet, Faramir.cl told me to get CAcert.org's gpg key and sign
> it as it is a Certificate Authority.

This handwaves the question, though, of _why_ you're choosing to trust
CAcert.org.

I have no evidence CAcert.org is untrustworthy.  At the same time, it's
not like they've ever bought me a beer, either.