Add random checkbox fill.

[emeryberger]

We currently use a dual approach to handle checkbox questions. Let's also randomize which boxes are checked and which are not. We can decide whether we can then dispense with the dual or not.

[dbarowy]

I revisited this over the weekend. The roadblock is that the API data structure I used does not allow for JavaScript, only a subset of XHTML. But this is possible using a newer, alternative structure that I experimented with over the summer. I will need to modify the existing templates, but then the random fill should be straightforward. I will probably need to do this anyway, since we will likely need new controls for the WoCMan input fields.