Allow running only one instance of application.

application/application.h

@@ -0,0 +1,21 @@
+#ifndef APPLICATION_H
+#define APPLICATION_H
+
+#include <QApplication>
+#include <QSharedMemory>
+
+class Application : public QApplication
+{
+    Q_OBJECT
+
+public:
+    Application(int &argc, char **argv);
+    ~Application();
+
+    bool lock();
+
+private:
+    QSharedMemory *m_single;
+};
+
+#endif // APPLICATION_H