Plot tracks on video frames

[roaldarbol]

To groundtruth the tracking (see that the points are where we believe they are, the effects of filtering etc.) it would be great to be able to output pictures and videos with the tracks overlaid. There's a few things here that need to be done.

• Extract video frames from video (has been done on the feature/draw-roi branch for which it will also be used)
• Function that draws them (e.g. plot_frame())
• That function should also be able to draw GIFs/short videos with overlay
• Should have a save-like parameter, so it will save the video and return the input data frame (needed to enable having it in a pipeline)