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/blackcore/airportdatareader.h

@@ -0,0 +1,71 @@
+/* Copyright (C) 2015
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKCORE_AIRPORTDATAREADER_H
+#define BLACKCORE_AIRPORTDATAREADER_H
+
+#include "blackcore/blackcoreexport.h"
+#include "blackcore/threadedreader.h"
+#include "blackcore/data/dbcaches.h"
+#include "blackmisc/aviation/airportlist.h"
+#include "blackmisc/network/entityflags.h"
+#include <QNetworkAccessManager>
+
+namespace BlackCore
+{
+    /**
+     * Reader for airport database.
+     */
+    class BLACKCORE_EXPORT CAirportDataReader : public CThreadedReader
+    {
+        Q_OBJECT
+
+    signals:
+        //! Emitted when data is parsed
+        void dataRead(BlackMisc::Network::CEntityFlags::Entity entity, BlackMisc::Network::CEntityFlags::ReadState state, int number);
+
+    public:
+        //! Constructor
+        CAirportDataReader(QObject* parent);
+
+        //! Read airports
+        void readInBackgroundThread();
+
+        //! Returns a list of all airports in the database.
+        //! \threadsafe
+        BlackMisc::Aviation::CAirportList getAirports() const;
+
+    private:
+        //! URL for airport list
+        BlackMisc::Network::CUrl getAirportsUrl() const;
+
+    private slots:
+        //! Parse downloaded JSON file
+        void ps_parseAirportData(QNetworkReply *nwReply);
+
+        //! Read Last-Modified header
+        void ps_parseAirportHeader(QNetworkReply *nwReply);
+
+        //! Read airports
+        void ps_readAirports();
+
+        //! Airport cache changed
+        void ps_airportCacheChanged();
+
+    private:
+        BlackMisc::CData<BlackCore::Data::DbAirportCache> m_airportCache {this, &CAirportDataReader::ps_airportCacheChanged};
+        mutable QReadWriteLock m_lock;
+        quint64 m_lastModified = 0; //!< When was data file updated, obtained from HTTP Last-Modified header, in ms from epoch
+
+    };
+} // ns
+
+#endif // guard