* Add the question number to the answer fields if it's available.
* Improve multiple choice question accessibility:
- Label the multiple choice question groups appropriately by
enclosing them in fieldset tags and applying sr-only legend tags to
label them.
- Apply Bootstrap form-check classes to the radio buttons, so they
are rendered better and become responsive as well. This also helps
avoid the use of the table element for layout purposes when
rendering horizontal multiple choice sub-questions.