Respect label_no_filter on checkbox labels.

Add code to respect the label_no_filter tag on checkboxes for Bootstrap and the Base widgets.

Bug demonstrated by having :

```
has_field 'agree_to_terms' => (
    type => 'Boolean',
    required => 1,
    label => 'I agree to the <a href="/terms" target="_new">Terms and Conditions</a>.',
    tags => { label_no_filter => 1 },
    required_message => 'You must agree to the Terms and Conditions.',
);
```