WIP issue-358 COPPA fix

Need to add validation and tidy things up. Also, maybe i should split all of this into a mixin?
Need spaces around the `+` symbols:
```js
datePickerEl.append('<option id="fxa-day + ' + i + 'value="' + i + ' " >' + i + ' </option>');
```

Plus, that.... doesn't look right around the `id` bit there. Should it be something like this?:
```js
datePickerEl.append('<option id="fxa-day-' + i + '" value="' + i + ' " >' + i + ' </option>');
```