Include Bbox and Area in GeoJSON Feature

[jeafreezy]

Is your feature request related to a problem? Please describe.

At the moment the GeoJSON feature of training areas doesn't have a bounding box and area. Therefore we handle the computation on the client.

Describe the solution you'd like

It would be great if each GeoJSON feature could have a bounding box, and the area could be included in the properties. This will eliminate this computation on the client. The bounding box is a valid property of a GeoJSON feature according to the GeoJSON spec.