- modify to use NIO buffer and add more documentation to transcoding process

...bluebutton/voiceconf/red5/media/AudioBroadcastStream.java

...luebutton/voiceconf/red5/media/SipToFlashAudioStream.java

...org/bigbluebutton/voiceconf/red5/media/net/RtpSocket.java

...f/red5/media/transcoder/NellyFlashToSipTranscoderImp.java

...f/red5/media/transcoder/NellySipToFlashTranscoderImp.java