also, the output video resolution is modified to the highest screen resolution shared during the conference, independently on the output video resolution set by the user; it was done to preserve the quality of the desktop sharing image; if there's no desktop sharing, the output video resolution is respected
Refactored the code that generates the video file used in the presentation playback. The problem with the sync of video sources was related to problems of precision inside FFmpeg (sometimes the script runs FFmpeg to trim video files, and the output video file trimmed sometimes was 3+ seconds bigger or smaller than the requested).
Also it's a little more modular, so it will be easier to expand functionality. The processing steps are more explicit now, and the logs are better now to understand the final output.
A new parameter on presentation.yml was added to enable the admin to add an offset for the audio stream - this is mainly useful when the session ran with h264, because the video takes longer for the client to encode, and then in the recording we can see the huge gap between audio and video.
