PTX stuff for parserRadioMultiAnswer

[Alex-Jordan]

I think I never got around to helping make parserRadioMultiAnswer work well for PreTeXt. These changes do that with my testing.

1. For the static PTX output, the wrapper around everything should be a ul. And the attributes being used here make PTX understand the ul is for answering something.
2. No need to have anything in between one button and the next.
3. The static PTX output looks bad to have a button, and then immediately the label like "A", "B", etc. I made the call to remove the "tag" there. The correct answer will still say things like "B", even though now the radio buttons are not labeled A, B, etc. But I think this is still understandable. And this is all for static PTX output where we don't really need the labels.

[drgrice1]

Thanks for doing this. Hopefully this means that usage of this macro is starting to take hold!