[Windows registry] Allow to clean all swift registry entries

* for uninstallation
* few users reported a hanging (white screen) swift issue, solved by "cleaning the registry"

see https://discordapp.com/channels/539048679160676382/539925070550794240/664557031784448010

src/blackgui/guiapplication.h

@@ -82,6 +82,12 @@ namespace BlackGui
         //! Own log categories
         static const BlackMisc::CLogCategoryList &getLogCategories();
 
+        //! Organization string used for settings, is the registry key under windows
+        static const QString &settingsOrganization();
+
+        //! Remove all registry entries
+        static bool removeAllWindowsSwiftRegistryEntries();
+
         //! Constructor
         CGuiApplication(const QString &applicationName = executable(), BlackMisc::CApplicationInfo::Application application = BlackMisc::CApplicationInfo::Unknown, const QPixmap &icon = BlackMisc::CIcons::swift64());