The backup procedure was changed to use a single file Periodical-backup.json.gz in the selected target location and not a folder de.arnowelzel.android.periodical with a file backup.json.gz inside. This makes it less confusing when transferring a backup to a new device. Old backups are still recognized and can still be restored. The new format will only be used when creating a new backup.
Code refactoring to avoid certain possible issues with deprecated APIs in newer Android versions.
Updated translations and help text to reflect the new backup procedure.