Allow unmanaged-files schema to detect mixed json

  The unmanaged-files schema now detects if its scope
  in the system description contains a mix of extracted
  and unextracted date and fails accordingly.
  The error messages of this schema however allow only
  for identification of the object in which the error occured
  not the specific item.
Merge pull request #163 from SUSE/unmanaged_schema

Allow unmanaged-files schema to detect mixed json