Add metadata to the coco car images

[flekschas]

Let's add the following properties to the car images from the COCO dataset:

• supercategory
• category
• annotationCount
• annotationArea

I suggest the following structure:

[
  {
    src: '...',
    id: '...',
    categories: [
      {
        supercategory: 'indoor',
        category: 'toothbrush',
        annotationAreas: [16.7, 4290.29], // combines annotationCount and annotationArea
      }
    ]
  }
]

With that information, we should be able to sort the images into a grid as follows:

• column: supercategory; row: category
• column: supercategory; row; annotation area or annotation count

Ideally, we'll have a separate sidebar where the user can choose the category for each axis. For data that is already categorical like the supercategory, category, or annotationAreas.length we just need a drop down menu. For annotationArea we probably need another input which defines the number of bins, i.e., divide annotationArea into 5 equally-sized bins.

[flekschas]

Fixed in 71454dc