Refactor SECLAL player into new threaded player class

The reason for moving the implementation out from CSoundGenerator into
its own class is, because CSoundGenerator was a very complex and
obscure class. It mixed many tasks in one place. CSelcalPlayer
is designed to play SELCALs only.

The following design changes have been made, compared to CSoundGenerator:
* Use pull mode instead of push mode. QBuffer is used as the QIODevice and
  is a wrapper around QByteArray. Therefore it is not necessary to
  implement our own QIODevice.
* Internally it uses a CThreadedSelcalPlayer to relieve the load of the
  main thread. CThreadedSelcalPlayer inherits CContinuousWorker, no
  low level QThread implementation was necessary.
* Push mode was not implemented.
* It is important that the QAudioOutput is allocated in the worker thread.
  QAudioOutput allocates internal objects, which cannot be moved to
  the worker thread.
* Data caching. The generated seclal audio data is cached.

refs #736

src/blacksound/selcalplayer.cpp

@@ -0,0 +1,46 @@
+/* Copyright (C) 2016
+ * 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.
+ */
+
+#include "selcalplayer.h"
+#include <QTimer>
+
+using namespace BlackMisc;
+using namespace BlackMisc::Aviation;
+using namespace BlackMisc::PhysicalQuantities;
+
+namespace BlackSound
+{
+    CSelcalPlayer::CSelcalPlayer(const QAudioDeviceInfo &device, QObject *parent)
+        : QObject(parent),
+          m_threadedPlayer(this, "CSelcalPlayer", device)
+    {
+        m_threadedPlayer.start();
+    }
+
+    CSelcalPlayer::~CSelcalPlayer()
+    {
+        m_threadedPlayer.quitAndWait();
+    }
+
+    void CSelcalPlayer::play(int volume, const BlackMisc::Aviation::CSelcal &selcal)
+    {
+        if (selcal.isValid())
+        {
+            QList<CFrequency> frequencies = selcal.getFrequencies();
+            Q_ASSERT(frequencies.size() == 4);
+            const BlackMisc::PhysicalQuantities::CTime oneSec(1000.0, BlackMisc::PhysicalQuantities::CTimeUnit::ms());
+            CTonePair t1(frequencies.at(0), frequencies.at(1), oneSec);
+            CTonePair t2({}, {}, oneSec / 5.0);
+            CTonePair t3(frequencies.at(2), frequencies.at(3), oneSec);
+            QList<CTonePair> tonePairs;
+            tonePairs << t1 << t2 << t3;
+            m_threadedPlayer.play(volume, tonePairs);
+        }
+    }
+}