For income events, break out the amount paid in routing fees vs the
total amount of the *invoice* that is paid.
Also printout these fees, when available, on listaccountevents
There's two situations where we're missing info.
One is we get a 'channel_closed' event (but there's no 'channel_open')
The other is a balance_snapshot arrives with information about accounts
that doesn't match what's already on disk. (For some of these cases, we
may be missing 'channel_open' events..)
In the easy case (no channel_open missing), we just figure out what the
niftynei