Dialog: Move call to _focusTabbable and triggering of open and focus events into the _show callback. Fixes #6756 - Dialog: show: "blind" with link in content doesn't animate properly. Fixes #8051 - Dialog: 'Explode' dialog animation causes crash in IE 6, 7 and 8. Fixes #4421 - Dialog: Focus lost from dialog which uses show-effect
Dialog Tests: Add test to ensure dialog keeps focus when clicking a modal overlay
Dialog Tests: Cleanup el -> element