Checked positions and geographic bounds

// Requires the updated native development runtime with aner.geo.
// Coordinates are illustrative city centers, not survey or GPS observations.
import aner.geo
import aner.units

let boulder: GeoPosition = geo.position(longitude: -105.2705, latitude: 40.0150)
let sanFrancisco = geo.position(longitude: -122.4194, latitude: 37.7749)
let losAngeles = geo.position(longitude: -118.2437, latitude: 34.0522)
let paloAlto = geo.position(longitude: -122.1430, latitude: 37.4419)
let boulderView: GeoExtent = geo.extent(west: -105.35, south: 39.95, east: -105.18, north: 40.10)

print(type(boulder))
print(boulder)
print(boulder.longitude())
print(boulder.latitude())
print(boulder.geojson())
print(boulderView.contains(boulder))
print(boulderView.contains(sanFrancisco))

// A named spherical model returns physical units rather than raw degrees.
let separation: Quantity<m> = geo.great_circle_distance(sanFrancisco, paloAlto)
print(separation.to("km"))
print(losAngeles.great_circle_distance(boulder).to("km"))
print(boulder.great_circle_distance(boulder) == 0.0@m)

// A wrapped extent represents a narrow Pacific interval around the dateline.
let pacific = geo.extent(170.0, -20.0, -170.0, 20.0)
print(pacific.contains(geo.position(179.0, 0.0)))
print(pacific.contains(geo.position(-179.0, 0.0)))
print(pacific.contains(geo.position(0.0, 0.0)))

// Keep station identity and observation metadata separate from its location.
class Station {
    public let id: String
    public let position: GeoPosition
    public let temperature: Point<degC>
}
let station = Station(id: "synthetic-boulder-01", position: boulder, temperature: 20.0@degC)
print(station.id)
print(station.position.geojson())
print(station.temperature)
let locations = List(boulder, sanFrancisco, losAngeles, paloAlto)
let restored: GeoPosition = cast<GeoPosition>(locations.get(0))
print(restored == boulder)

// No longitude/latitude vector arithmetic, geocoder or implicit CRS conversion.
// Great-circle distance uses a 6371008.8m sphere, ignoring altitude/ellipsoid.
// See docs/GEOGRAPHIC_TYPES.md before selecting a method for scientific analysis.