loadLog should verify the hashes (and signatures) in the log, and
refuse to use logs that are not valid proofs of a session.

(--replay and --graphvis need this; server's use of loadLog does not)

Everything else in debug-me checks a session's proof as it goes.
And, everything that saves a log file checks the proof as it goes,
so perhaps this is not actually necessary?

> Yeah, let's not. Instead, --verify can be used. [[done]] --[[Joey]]
