Override hashCode and overload == operator for GeoJSON types

[lukas-h]

• Position
• BBox
• Point
• MultiPoint
• LineString
• MultiLineString
• Polygon
• MultiPolygon
• GeometryCollection
• Feature
• FeatureCollection

as discussed in #43

[tobrun]

👍 on this issue, to be able to scale the functionality of this library, this is a must have feature.

For context, was adding a new functionality and couldn't easily compare two FeatureCollections:

GeoJSONObject actual = flip(GeoJSONObject.fromJson(json));
GeoJSONObject expected = GeoJSONObject.fromJson(flippedJson);
expect(actual, expected);

[lukas-h]

Hi @tobrun,

we are currently working on a separate library that offers equality functions for the more complex data types of geojson.
https://github.com/dartclub/turf_equality
The lib is based on: https://www.npmjs.com/package/geojson-equality

We have to find a way to combine the new lib into turf_dart at a later point.

And I still think it's a problem if we override == with a really performance hungry function that can compare e.g. highly nested FeatureCollections.

CC @armantorkzaban

[lukas-h]

–> DECISION: What should be done with booleanEqual?