API uses uuid as reference

When the API returns lists of objects (or perhaps elsewhere) that reference the same object (for example owner of a dataset), the second reference will not be provided as an object in JSON, but only the uuid of the referred-to object.

Example

The owner first provided as an object in the dataset with id 2 (and it has uuid 35c5849a-39d7-400d-a242-726b12c92244).

The second occurrence of the same owner for dataset with id 3 only has a reference "owner": "35c5849a-39d7-400d-a242-726b12c92244".

{
	"content": [{
		"id": 2,
		"version": 7,		
		"uuid": "f5245842-2567-490a-a127-aa35b85d1128",
		"owner": {
			"uuid": "35c5849a-39d7-400d-a242-726b12c92244",
			"id": 1,
			"shortName": "CIP",
			"name": "International Potato Centre",
			"_permissions": {
				"create": true,
				"read": true,
				"write": true,
				"delete": true,
				"manage": true
			}
		},
		...
		"_permissions": {
			"create": true,
			...
		}
	}, {
		"id": 3,
		"version": 6,
		"owner": "35c5849a-39d7-400d-a242-726b12c92244",
		...
	}, {
		"id": 4,
		"version": 5,
		"owner": "35c5849a-39d7-400d-a242-726b12c92244",
		...
	}],
	"totalPages": 1,
	...
}

Update the reducer so that it will map the references and convert them to proper objects.

Without this, the application will break with JS errors.