Fix Bug 1083481 -  <details> fallback JavaScript and CSS is not #a11y

Existing code was good but was throwing an error. Updated test for Opera to be stand alone and not rely on something we probably removed.

Added ARIA roles.

Tweaked CSS.

Testing:
- test both FireFox and Chrome since Chrome does support details and FF doesn't
- details should expand on both space and enter
Separate "var" for each variable, por favor