Draft: Standardized formats when writing bounding boxes to JSON API

This MR proposes two standardized formats for writing bounding boxes to the JSON API: GeoJSON because it integrates nicely into an existing JSON-based schema and WKT because it is more succinct.

However, personally I am not happy with either formats as they do not support AABB/rectangles natively and hence have to represent them as general polygons which is highly redundant compared to our "native" representation. Hence I would actually prefer we keep our "native" representation and convert into standardized formats only when necessary.