Added geometry field to Location

As the Datahub provides geometries instead of boundingBoxes (which may be points, polygons, etc) we should update our metadata schema.

I added a new field 'geometry' to Location.

Furthermore, I set both 'geometry' and 'boundingBox' as not required, so that either of them may be used. I believe it is not possible to require either/or. We could always calculate the boundingBox from geometry, of course, and vice versa set the geometry based on boundingBox.