UI updates

- add import dialog
  this is more complex than I thought
- added scope exit
  grammar sugar
- main dialog is now linked to import dialog
- importer citra file path is fixed
- importer now reports maximum size
- file util is improved with GetDirectoryTreeSize

src/frontend/main.h

@@ -23,6 +23,7 @@ private:
     void LoadPresetConfig();
     void ShowAdvanced();
     void HideAdvanced();
+    Core::Config GetCurrentConfig();
 
     std::vector<Core::Config> preset_config_list;
     std::unique_ptr<Ui::MainDialog> ui;