Listen for SCSessionGotNoAudio in sip_audio_session.py

darcs-hash:20090216142024-58103-0c0c1b8e2f2e3d966d5c20062a9fe3ed58116f4c
Implemented audio to recording .wav file on Session object

- Added on_hold property with aggregates both on_hold_by_* attributes
- Added audio_recording_file_name property which points to the file
  currently being recorded to
- Added start_recording_audio(dir, file_name=None) method, automatically
  generates useful file name if it is None
- Added stop_recording_audio() method
- Added SCSessionStartedRecordingAudio and SCSessioNStoppedRecordingAudio
  methods, both with file_name attribute
- Automatically stop recording when session audio stops, pause recording
  when on hold

darcs-hash:20090216151120-58103-72d696db6845e3176a966e80b484588f78a5a8b5