bootstrap_field show_label not honoured for checkboxes

[rhelms]

Similar to zostera/django-bootstrap3#414, the show_label=False directive is ignored for checkbox fields.

{% bootstrap_field editabletext_form.DELETE layout="horizontal" show_label=False %}

renders

<div class="form-group row">
    <label class="col-md-3 col-form-label sr-only" for="id_detectedtext_set-0-DELETE">&nbsp;</label> 
    <div class="col-md-9">
        <div class="form-check">
            <input type="checkbox" name="detectedtext_set-0-DELETE" class="form-check-input" id="id_detectedtext_set-0-DELETE">
            <label class="form-check-label" for="id_detectedtext_set-0-DELETE">Delete</label>
        </div>
    </div>
</div>

Whilst the first <label> is fine, should sr-only be supported (I haven't actually checked if it is), the second <label> should be suppressed, or also applied with the sr-only class.

[jannh]

Btw: The same goes for the label_class attribute for checkboxes. If a different label_class is specified in the bootstrap_field, it does not appear in the html (will always be "form-check-label").