Make `iati-activities` or `iati-organisations` mandatory in an IATI file

It has been spotted that the root <iati-activities> or <iati-organisations> elements are not set by the IATI schemas as a mandatory component of an IATI file. Therefore, a file containing only the following would pass validation in the v2.02 schema:

<title>
   <narrative>Activity title</narrative>
   <narrative xml:lang="fr">Titre de l'activité</narrative>
   <narrative xml:lang="es">Título de la actividad</narrative>
</title>

This type of thing is referred to as a type of ‘XML error’ on the Dashboard, under 'Files with non-standard roots’.

This would likely require a major version upgrade as the change would not be backwardly compatible.