Add prototype GeoJSON objects and converts from Nominatim search results

[rolyhudson]

Description:

As per the bigger description in #68
Adding prototype set of GeoJSON objects and methods to convert from the nominatim query result (GeoJSON formatted) to those objects.

[rolyhudson]

Currently prototyped in here are an initial object model proposal that looks like this:

And initial converts currently set up:

We want geometry from these objects but what should the default be? We could do:

1. Simple mapping of Longitude to X and Latitude to Y gives something to look at but the distortion and units meaningless making measurement impossible
2. A projection to Web Mercator as per typical online mapping
3. Straight to universal transverse mercator (probably the best) - we already can do this but need to figure out the mapping when an object spans multiple zones.

In some cases we'll need to serialize back to the original geojson format for pushing into files and database. We'll need a custom serialiser to do so I believe.

@rwemay @al-fisher any thoughts on this?

[al-fisher]

This looks great @rolyhudson

Geospatial_oM looks good and makes sense

Agree default should probably be universal transverse mercator - ready to be in a form to carry out geometrical measurements, distances, angles etc.
But with potential to implement any other projections on convert for special applications I suppose