Check wether GeoJSON should be returned as string

[eFrane]

Currently GeoJSON fields are returned in their native
glib-json representation which can be difficult to use
for programmers accessing liboparl via gobject-introspection
in e.g. python.

We should do some research on wether it would be better
to return the full GeoJSON string and let the user deal
with it however they wish.

[konstin]

While I haven't looked at the details, I suggest returning json as this is the data type. It might also be reasonable to include a geojson validator in liboparl.

[eFrane]

@konstin: Do you mean as JSON String or as JSON Object?