Bug 36909: Eliminate duplicate ID in cookie consent markup

Bug 36909: Eliminate duplicate ID in cookie consent markup

This patch changes markup and CSS in the OPAC and staff client to
eliminate HTML validator warnings about duplicate ids.

To test, apply the patch and rebuild all CSS (Bug 36909: Eliminate
duplicate ID in cookie consent markup).

- If necessary, set the "CookieConsent" system preference to "Require."
- Open the OPAC in a new private window (to prevent previous consents
  from hiding the consent messages).
- You should see a cookie consent bar across the bottom of the page. It
  should look correct, and its contents should reflow well at various
  browser widths.
- Click "Accept all cookies."
- In the header you should now see a "Your cookies" link.
- Click it and confirm that the contents of the modal look correct and
  reflow well at various browser widths.

- Perform the same tests in the staff interface.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>