Backup world file saved without .zip

The bug

"Don't forget to backup this world before you load it in this snapshot."

The saved file names are not attaching the .zip, they are functional zip files once the .zip is added back to their names.

Code analysis

LevelStorage.backupLevel(final String name) now uses WorldNameProvider.transformWorldName(path, string) to determine the world name, but does not append ".zip" anymore.