Make GroovePlayer a singleton to avoid being created for each browser. Add login UI component to eventually hold landing screen. Actually start server with initial interface.

src/GroovePlayer.h

@@ -22,6 +22,15 @@
 
 class GroovePlayer
 {
+public:
+    static GroovePlayer* getInstance() {
+        static GroovePlayer instance;
+        return &instance;
+    };
+    GroovePlayer(GroovePlayer const&) = delete;
+    void operator=(GroovePlayer const&) = delete;
+private:
+    GroovePlayer();
 };
 
 #endif // GROOVEPLAYER_H