Allow for variable depth taxonomy

This is an extension to COEL-130 on improved JSON coding (so designed to be on the deferred list for now) and comes from a recent academic workshop on taxonomies of behaviour.
The integer array that references the model could be of variable length both less than 4 (for existing low levels of granularity) and greater than 4 (for future more granular expansion). The minimum length of the array would be 1.