Make data re-usable (e.g. GeoJSON)

[m-mohr]

Originates from Open-EO/openeo-processes#226

Anyway, specifying the bbox twice is not an issue if you use the python client, but with the Web Editor could be, since you would need to manually select the same area, or copy the coordinates in the json process graph which is not user friendly.

So there should be a simplification for such use cases, e.g.

• allow GeoJSON blocks that can be used as inputs
• Give users a choice to select previously used GeoJSON (or get it from load_collection)
• Make copy/paste easier
• ...?