QPID-????: Tidy up
- Remove unused function getBuffered() of ConnectionOutputHandler
- Stop SessionContext and AggregateOutput from needlessly implementing
  the OutputControl interface
QPID-4854: Make the protocol negotiation timeout actually relate to
the protocol negotiation!
QPID-????: Remove unused members in Connector interface
QPID-????: Tidy-up remove OutputHandler and directly use FrameHandler
QPID-????: Tidy up broker::Connection
- Clean up code for accounting for sent frames
- merged Connection and ConnectionState into Connection
- removed idleOut member of TimeoutHandler interface
  the entire interface could actually go.