Update valuesviewset to handle PATCH.
Update valuesviewset to handle PATCH.

learningequality/kolibri,mrpau/kolibri,mrpau/kolibri,indirectlylit/kolibri,indirectlylit/kolibri,mrpau/kolibri,learningequality/kolibri,mrpau/kolibri,learningequality/kolibri,learningequality/kolibri,indirectlylit/kolibri,indirectlylit/kolibri