Add singleapplication

GPClient/main.cpp

@@ -1,11 +1,13 @@
+#include "singleapplication.h"
 #include "gpclient.h"
 
-#include <QApplication>
-
 int main(int argc, char *argv[])
 {
-    QApplication a(argc, argv);
+    SingleApplication app(argc, argv);
     GPClient w;
     w.show();
-    return a.exec();
+
+    QObject::connect(&app, &SingleApplication::instanceStarted, &w, &GPClient::raise);
+
+    return app.exec();
 }