Use a more efficient means for recording Sibernetic simulation video

[mwatts15]

Current Docker container uses an ffmpeg screen recording feature (x11grab) to record Sibernetic simulation video. This method of recording brings in several X11 dependencies which are not otherwise necessary which complicates maintenance of the Docker image. Rather than this, it would be preferable to provide other means of recording a video of the simulation, possibly as a separate operation from the master_openworm.py script execution.

Relates to: openworm/sibernetic#182