Add coco style annotations

[23pointsNorth]

Hi @thsant ,

This is a PR that converts the existing annotations to coco-style annotations of the dataset.

The test/train split is maintained with the following considerations:

• X_bbox_instances.json -> all of the bounding box annotations within the X split (incl. bbox and those of the instance segmentation box ones)
• X_polygon_instances.json -> all of the annotations that contain an instance semgnentation mask within split X.

The annotations can be confirmed with external tools like e.g. https://github.com/trsvchn/coco-viewer by specifying an annotations file and the ./data/ folder as the image folder.

[thsant]

Hi @23pointsNorth , thank you very much. I saw a preview in CVAT and the annotations look fine. My only concern is about bunches crossed by a vine branch (the COCO annotations are showing two bunches instead a single bunch with an occluding branch). When a finish the evaluation, I will update the README, including credits to your contributions.