Toggle: aligned WAI-ARIA attributes with recommendation

WAI-ARIA attributes are now being set based on accordion widget
recommendations: http://www.w3.org/TR/wai-aria-practices/#accordion
Toggle: updated working examples

1. English/French updated with new accordion markup.
2. Added TOC and configuration section to English.
3. Added TOC to French (todo: translate configuration section).
Merge pull request #3762 from patheard/accordion-aria

Toggle: aligned WAI-ARIA attributes with W3C recommendation