GH-3012 add --offline and --name arguments

These allow launching offline with a specified name from the command line.

launcher/LaunchController.h

@@ -28,6 +28,10 @@ public:
         m_online = online;
     }
 
+    void setOfflineName(const QString &offlineName) {
+        m_offlineName = offlineName;
+    }
+
     void setProfiler(BaseProfilerFactory *profiler) {
         m_profiler = profiler;
     }
@@ -66,6 +70,7 @@ private slots:
 private:
     BaseProfilerFactory *m_profiler = nullptr;
     bool m_online = true;
+    QString m_offlineName;
     InstancePtr m_instance;
     QWidget * m_parentWidget = nullptr;
     InstanceWindow *m_console = nullptr;