Annotation export format streamline

[pradeepsen99]

Currently the JSON exported by AVAT is a simple JSON dump into a massive array of length=frame number. This is inefficient on storage and cumbersome to work with. Instead, we can streamline this by using a nested json approach where each array element has a frame identifier indicating the frame it's from and the redux store smartly grabs the data upon upload.

Potential data format:

{
  frame_number: 1
  Annotation_type: “bounding_box”
  Dimensions: ….data dump of coordinates for box/segmentation
}