[iso19139] check all geometries, for valid bbox

[pvgenuchten]

To parse this real-world-example, 2 options exist:

• check all extent-geometries until a valid is found (in stead of first one, this is similar to how temporal extent is extracted)
• support the gml-polygon (and also point/polyline)

707a02ac-9240-4a2d-afbd-395b69756534.zip