implement basic OSM types and option to return them

[mvexel]

Right now we return raw-ish data (JSON / dict, GeoJSON, CSV) which is fine but puts the burden of parsing it into OSM features on the user. Since extracting OSM features is the first thing anyone would probably want to do, it would seem to make sense to implement basic OSM types (Node, Way, Relation) and offer the option to return collections of those instead.

We could borrow from https://github.com/osmlab/osmdiff/blob/master/src/osmdiff/osm/osm.py

(As a bonus, these already implement __geo_interface__, see #147)

[mvexel]

I updated osmdiff recently and the __geo_interface__ interfaces are in better shape now. They still require some testing, especially relations.

I'd love to consider this for the next point version.

[Vectorial1024]

I noticed another Python library overpy, it seems to provide some basic util functions to loop over overpass results. Would overpy be good enough for this?

[mvexel]

I don't know about overpy more that that it offers comparable functionality to this library. If it fits your use case, by all means go ahead and use that (for now)!