Replace JQTE with textarea in question page

Now that we're not using JQTE's features (like bold and italic) at all,
we can replace it with a plain textarea. This has a couple of benefits:
E2E testing becomes simpler, and more importantly, there's a subtle bug
that becomes impossible. Because clearing the Angular model was not
clearing the visible-to-the-user JQTE element, the user could think
their answer was still in the editor when in fact it was not. This could
lead to the following set of steps, all quite sensible:

1) User creates an answer.
2) User edits the answer they just created.
3) User decides they don't like their edit, so they delete the answer.
4) User sees their original answer still in "New Answer" edit box, and
   clicks "Done" underneath it to re-submit their original answer.

What the user expects at that point is that their original answer will
be re-submitted. But the Angular model is empty, even though the div the
user is seeing is not, so what actually happens is that a blank answer
is submitted, and whatever the user had originally typed ends up lost.
Getting rid of JQTE and replacing it with a plain textarea (which *does*
update itself when the Angular model changes) means the user won't think
their original answer is still around when in fact it isn't.