GeoLatLng constructor
Implementation
GeoLatLng(this._latitude, this._longitude) {
GValidate.inclusiveBetween(-90.0,90.0,_latitude,"Latitude must be between -90 and 90 degrees but was $_latitude");
GValidate.inclusiveBetween(-180.0,180.0,_longitude,"Longitude must be between -90 and 90 degrees but was $_longitude");
}