Bug 1032629 - APN Settings UX refresh

https://bugzilla.mozilla.org/show_bug.cgi?id=1032629
We may need this comparison function to make sure custom options will be put on the top.

```javascript
items.sort(function(apnItemA, apnItemB) {
  if (apnItemA._category === ApnItem.APN_CATEGORY.CUSTOM ||
    apnItemB._category === ApnItem.APN_CATEGORY.CUSTOM) {
    return 1;
  }
  else {
    return -1;
  }
});
```