Issue #15 Added CPassiveObserver and CPassiveMutator

These implement a many-to-many publish/subscribe pattern.

src/blackmisc/sharedstate/passiveobserver.cpp

@@ -0,0 +1,36 @@
+/* Copyright (C) 2017
+ * 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. 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
+
+#include "blackmisc/sharedstate/passiveobserver.h"
+
+namespace BlackMisc
+{
+    namespace SharedState
+    {
+        void CPassiveObserver::setEventSubscription(const CVariant &param)
+        {
+            QMutexLocker lock(&m_eventSubscriptionMutex);
+            m_eventSubscription = param;
+            lock.unlock();
+            emit eventSubscriptionChanged(param);
+        }
+
+        CVariant CPassiveObserver::eventSubscription() const
+        {
+            QMutexLocker lock(&m_eventSubscriptionMutex);
+            return m_eventSubscription;
+        }
+
+        void CPassiveObserver::handleEvent(const CVariant& param) const
+        {
+            m_eventHandler(param);
+        }
+    }
+}