Ensure that SS and NS contain unique values only

Instead of `unique`ing the whole array, probably more efficient to do something like:

```js
if (!item[attr][type]) item[attr][type] = []
item[attr][type] = item[attr][type].concat(data.AttributeUpdates[attr].Value[type].filter(function(a) {
  !~item[attr][type].indexOf(a)
}))
```