Convert support/submit.bml+widget to controller+TT

- DW::Controller::Support::Submit, views/support/submit.tt, and
  views/support/submit.tt.text

  Note 3 deviations from the original HTML here:

  1- I didn't bother to include an id= in the div because the original id
     changes between reloads, and thus isn't usable for styling, and there's
     no JS making use of it that I can see.

  2- I got rid of the unused, incorrect classname per request.

  3- Also per request, I used DW::FormErrors (with some minor deviations
     from recommended use to get errors to display since this isn't a
     Foundation page) instead of reverse-engineering the HTML the original
     BML magic used..

  Also, this doesn't implement the support_request_cat_extra_text hook
  (which wasn't defined anywhere that I could see), or the invisible
  category system half-implemented in LJ::Widget::SubmitRequest->category
  and LJ::Widget::SubmitRequest->render_body (as the one existing subclass
  doesn't override it).

- Add example of CAPTCHA use in controllers+templates to DW::Captcha. While
  I'm at it, get rid of BML dependency.

- Get rid of more strings while I'm at it. These were never used as far as I
  can tell.

- Remove widget files no longer needed: LJ::Widget::SubmitRequest::Support
  and LJ::Widget::SubmitRequest

Fixes #963