Heist: add wrapping div around label/input pairs for dfInputRadio

The way the current code is, the labels / inputs are just sent out one after another, which makes it really hard to style, as you can't apply styling to the pairs as units, because the markup looks like:

    <input ...>
    <label ...>
    <input ...>
    <label ...>
    ...

So I added a `<div class="radio">` around each pair, so it looks like

    <div class="radio">
        <input ...>
        <label ...>
    </div>
    <div class="radio">
        <input ...>
        <label ...>
    </div>
    ...

Which can by styled as inline, if desired.