Create a log entry for every HTTP transaction.

Create a log entry for every HTTP transaction.

These are built into a struct and passed to a 'consume' method which
currently does nothing with them.

In the immediate short term, I want to add a --debug option which
writes them to a log file on disk, so I can look at a misbehaving
session and see what went wrong.

In the longer term, I think I might also want to keep a rolling buffer
of these log entries, and make it accessible through the Logs Menu.