Inline Analytics

  Display of answer distribution graphics inline on the problem page
  for instructors.

  Problem types supported for graphics:
    - MultipleChoiceResponse
    - ChoiceResponse

  Problem types supported for line item display:
    - OptionResponse
    - NumericalResponse
    - StringResponse
    - FormulaResponse
    via setting

Internal review only for now.
This line is pretty long. Since we're already splitting onto multiple
lines, can we break up this line too?

```javascript
tr = $('<tr><td class="answer_box" title="' +
    choiceText[currentIndex] + '">' + (currentIndex + 1) +
    '</td><td class="answer_box ' + answerClass +
    '"><span class="dot"></span></td><td class="answer_box">0</td><td class="answer_box">0%</td></tr>'
);
```

I don't mind the long string literal; it's a single chunk of text (no variables).