Efficient Frame Extraction

[sjz38]

The preferred method to extract frames is to utilize the jpg's magic starting and ending bytes. Since we need the image files to have their timestamps in the filename, this can be done in two ways.

1. Extract all frames from the mjpeg file byte buffer after the mjpeg has been recorded. We will be able to calculate the timestamp of each frame based on the output of raw_observation().
2. (Possibly) Perform image extraction in the same manner as the picamera example (https://picamera.readthedocs.io/en/release-1.13/recipes2.html#rapid-capture-and-processing), and add the timestamps to the files afterward by renaming the files.