v4 ideas - simplifying the API

[gmaclennan]

I think we can simplify some of the API, and move higher-level API calls into a separate module, something like osm-p2p-api. This is where all the checks can take place to maintain data integrity (not deleting nodes that are part of a way etc.). Much of this work is already in digidem/osm-p2p-server/api.

• Remove osm.create() - functionality is in osm.put().
• Remove osm.getChanges() - this is not particularly useful, and the higher-level functionality is in the api from osm-p2p-server.
• Merge osm.query() and osm.queryStream() to a single method that returns a stream when no callback is passed.
• Change the property refs on ways to nodes to match OSM JSON format.