Add the methods `set()`, `persist()` and `remove()` to the `Config` class
Use the new `Config` methods in the front controllers
Use the new `Config` methods in the calendar extension
Use the new `Config` methods in the comments extension
Use the new `Config` methods in the core extension
Use the new `Config` methods in the FAQ extension
Use the new `Config` methods in the listing extension
Use the new `Config` methods in the news extension
Use the new `Config` methods in the newletter extension
Use the new `Config` methods in the repository extension
Wrap things up
Merge branch 'feature/config-usage' into develop