GetKeyFrames: Process scene detection on all given frames, rank-orders, returns top N results. Always includes first frame. Also returns labeled images.

MakeGrid: Plots given images on a grid. Calculates number of rows and columns for most even aspect ratio.

For concurrent frame generation. Creates potentially massive image.
Images are resized to be evenly-divisible by rows, columns, and 8 (to prevent "resize wobble").
Empty cells are padded with repeats of last image. Black space frustrates generation.

BreakGrid: Breaks given image grid(s) back into individual images. Good practice to use cows/columns output from MakeGrid.