Collapse accessability

Added tabIndex aria attribute to collapse plugin

Added tab-role, aria-selected, and aria-controls into the collapse html
docs.

Added support for toggling aria-expanded, aria-selected, and
aria-hidden
via the javascript collapse events.

References issue #13555

Sweet example at
http://accessibility.athena-ict.com/aria/examples/tabpanel2.shtml
added more role="tab"'s
Removed unneccessary tabIndex's, moved aria-expanded to trigger element
removed aria-selected
Small fixes as suggested by @hnrch02 in pull # 14153