Toggle: plugin behaviour fixes

1. Fix first click on elements that toggle themselves.
2. Fix setAriaControls to set unique IDs on elements that don't
   have an ID defined.
3. Group toggle elements no longer default to "type: on" (fixes #3711)
Toggle: update examples to show group with "type: on"
Merge pull request #3720 from patheard/accordion

Toggle: plugin behaviour fixes