Update Posetrack export

[dari1495]

Since objects changed, this is a reminder for me to:

• Check if the export still works
• Update it to include the new stuff

[dari1495]

The objects (bbox, bbox_head, persons) are sometimes created in different objects, but they should be part of the same object under names (bbox, bbox_head, keypoints) respectively.

This is how it looks now:

{
         "category_id":1,
         "track_id":0,
         "person_id":2,
         "bbox":[
            699.136236545022,
            217.90299536628416,
            170.72731712386826,
            462.8384819064431
         ],
         "id":1000002000000,
         "image_id":10000020000,
         "scores":[   ]
      }

And this is how it should look like

{
        {
            "category_id": 1, 
            "track_id": 0, 
            "person_id": 2,
            "bbox": [
                766.875, 
                155.92832185499998, 
                139.75, 
                551.16798399000004
            ], 
            "bbox_head": [
                780, 
                211, 
                53, 
                68
            ],
            "keypoints": [
                806, 
                250, 
                1, 
                (...more points...)
                814, 
                643.5, 
                1
            ],
            "id": 2000002006000,
            "image_id": 20000020060, 
            "scores": [   ]
        }
      }