Allow yii\boostrap\ActiveField to customize the DIV and the LABEL tag around the checkboxList's inputs

If inline attribute is not set ( https://github.com/yiisoft/yii2/blob/master/extensions/bootstrap/ActiveField.php#97 ) there's no possibility to customize tags around input for the activeField checkboxList.
This patch allows to set the attributes even to DIV and to LABEL.

**How to use**

Inside *itemOptions*
add *containerOptions* to set the DIV attributes 
and/or
add *labelOptions* to set the LABEL attributes

```
\yii\bootstrap\ActiveForm::checkboxList(
    $check_box_array, [
        'class' => "outside-class",
        'itemOptions' => [
            'containerOptions' => [
                'class' => "div-wrapper-class",
            ],
            'labelOptions'     => [
                'class' => 'label-wrapper-class'
            ],
            'class' => 'input-tag-class',
        ]
    ]);
```

**The effects**
From this HTML
```
<div id="queryform-answermultiple" class="outside-class">
    <div class="checkbox">  // <-----------------------
        <label>   // <-----------------------
            <input type="checkbox" class="input-tag-class" name="QueryForm[answerMultiple][]" value="123">
        </label>
    </div>
    <div class="checkbox">
        <label>
            <input type="checkbox" class="input-tag-class" name="QueryForm[answerMultiple][]" value="456">
        </label>
    </div>
</div>
```

To this HTML
```
<div id="queryform-answermultiple" class="outside-class">
    <div class="div-wrapper-class">   // <-----------------------
        <label class="label-wrapper-class" >   // <-----------------------
            <input type="checkbox" class="input-tag-class" name="QueryForm[answerMultiple][]" value="414">
        </label>
    </div>
    <div class="div-wrapper-class">
        <label class="label-wrapper-class">
            <input type="checkbox" class="input-tag-class" name="QueryForm[answerMultiple][]" value="415">
        </label>
    </div>
</div>
```