One tip for render custom label

Change this 

```php
$this->parts['{input}'] = Html::activeTextInput($this->model, $this->attribute, $this->inputOptions);
```

For this 

```php
$this->parts['{input}'] = Html::activeInput($this->inputOptions['type'], $this->model, $this->attribute, $this->inputOptions);
```

And field exemple

```php
$form->field($model, 'termsconditions', [
            'labelOptions' => [
                'label' => Yii->t('app','I agree to the ') . \yii\helpers\Html::a( Yii->t('app','Terms and Conditions'), ['#'])
            ],
            'inputOptions' => [
                'type' => 'checkbox',
                'uncheck'=>0,
            ]
        ]) 
```