Fix #87 - Only allow selecting enabled languages

- Retrieve disabled_languages in system configs
- Filter disabled languages from the list of selectable languages
- If store languages is disabled reset to default language

config/services/legacy/exposed_system_configs.yaml

@@ -4,6 +4,7 @@ parameters:
     passwordsetting:
       forgotpasswordON: true
     languages: true
+    disabled_languages: true
     default_module: true
     default_theme: true
     module_name_map: true