citra_qt: add Clear Recent Files menu action

I had to edit a bit of the Restart action so that it does not go wrong because recent files are cleared.

src/citra_qt/main.h

@@ -205,6 +205,8 @@ private:
     std::unique_ptr<EmuThread> emu_thread;
     // The title of the game currently running
     QString game_title;
+    // The path to the game currently running
+    QString game_path;
 
     // Debugger panes
     ProfilerWidget* profilerWidget;