Uses of uuid and eui64 should be factored out into their own schemas

[andrewbonney]

In order to reduce duplication (and potentially incorrect) pattern specifications for UUIDs, EUI64s etc these should be factored out of the JSON schema definitions into their own file or files.

These would then be referenced as follows for example:

"node_id": {
  "description": "ID of the Node",
  "$ref": "uuid.json"
}

If a single file is preferred for these definitions then the following approach could be used:

"$ref": "core.json#/definitions/uuid"