refs #650 Implement CAirportDataReader

* Add BlackCore::CAirportDataReader class
* Add cache traits for airport list
* Add corresponding WebReaderFlag
* Add CAirport::convertFromDatabaseJson()
* Add CApplication::headerFromNetwork() to handle HTTP HEAD method

src/blackmisc/aviation/airportlist.cpp

@@ -44,5 +44,19 @@ namespace BlackMisc
             return this->findFirstByOrDefault(&CAirport::getIcao, icao, ifNotFound);
         }
 
+        CAirportList CAirportList::fromDatabaseJson(const QJsonArray &json)
+        {
+            CAirportList airports;
+            for (const QJsonValue& value: json)
+            {
+                QJsonObject object = value.toObject();
+                CAirport airport;
+                airport.fromDatabaseJson(object);
+                airports.push_back(airport);
+            }
+
+            return airports;
+        }
+
     } // namespace
 } // namespace