feat: mdv5a coco data prep

[nayan-mehta]

Hi Dan,

Thanks for the quick review, updated the following. Do let me know if this looks good :)

• coco_download.py: Downloads train+val+test
• coco_data_prep.py:
  • Takes in the datasetYear as arg (e.g. train2017)
  • Filters person and vehicles images and annotations
  • Converts COCO to YOLOv5 format

[agentmorris]

Looks great! You marked this as a draft and indicated "WIP" in your comment, so it looks like you're just looking for a quick review now, not a merge. The download script and Python script both ran without any issues, I see no concerns.

One quick note: although all of this data would be in the train split from MegaDetector's perspective, there's no reason not to use the train+val+test data from COCO, rather than just the train data. It doesn't change the code at all, just a couple more lines in the download script.

For my two cents, I would probably do the download in Python also, just to keep things all in one place, but the shell script is fine too.

Thanks!