Further isolate Configuration logic to PadSession
Further isolate Configuration logic to PadSession

This continues what commit 6f02e1d09 started.

* onetime
  (Configuration): Move definition to before PadSession.
  (Configuration.__init__): Initialize new field self._pad_session.
  (PadSession.__init__): Instead of taking a Configuration object,
    take a configuration area path and instantiate the object from it.
    Also, take a new no_trace argument.
  (PadSession.finish): Save the configuration, unless no_trace.
  (main): Set up PadSession in the new way.  Remove unused --debug
    option that printed config.

kfogel/OneTime,kfogel/OneTime