Data format cleanup: Introduce "status" for config_files

Introduce a "status" attribute for files in the config_files scope. This
mimics a similar attribute in the changed_managed_files scope. For now,
the value is always "changed" as we don't detect errors in
ConfigFilesInspector in the same way as in ChangedManagedFilesInspector.
Merge pull request #72 from SUSE/data-cleanup-config-files-status

Data format cleanup: Introduce "status" for config_files