Session base class now handles the engine events exclusively. It notifies
derived session types using dedicated "attached" and "detached" events.
Couple of bugs was fixed along the way.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
Fix in termination of session attached to a REP socket.
Several fixes of session termination in case of disconnection.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>