Use core's filename transliteration

[chrfritsch]

Make sure these boxes are checked before submitting your pull request - thank you!

• [ ] All coding styles are fulfilled. (How to check for cs issues?)
• [ ] All tests are running locally. (How to run the test?)
• [ ] Necessary update hooks are provided.
• [ ] User roles have correct access for new introduced permission.
• [ ] Every thunder module has a README.md in its root. Follow this guidelines, but we don't need every topic.
• [ ] Code is covered with well-balanced amount of inline comments.

If you are really awesome, then your feature is covered by additional tests. Well done!