pettycoin: record input and output times, and status.

This should help debug issue #32 (connections lost between nodes).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
getpeerinfo: new RPC command.

Lots of information to help us debug issue #32.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>