refs #372 Add audio mixer interface and vatlib implementation

This class is an audio router. In order to route audio connect a
producer to an input port and a consumer to an output port. The
connection is later established by making the mixer connection
between an input and an output port.

src/blackcore/audio_mixer.cpp

@@ -0,0 +1,16 @@
+/* Copyright (C) 2014
+ * 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 "audio_mixer.h"
+
+namespace BlackCore
+{
+    IAudioMixer::IAudioMixer(QObject *parent) : QObject(parent)
+    { }
+}