change path control message inner message response to take just a
string, which will be a bt-encoded response with an early key for
status. If there is a timeout we pass a bt dict that only has that as
the status, else the response we de-onioned should have either an OK
status or some other error.
change messages to use new status key
correctly call Path::EnterState on path build response
- `::handle_message` is transposed; Rather than the message calling the method and taking a reference to the router, the router should have a handle_message method and take a reference to the message
- `::EndcodeBuffer` takes a string reference, to which the result of `::bt_encode()` is assigned