Button icon span

Working branch right now up for functional review for button re-write demo at http://view.jqueryui.com/button-icon-span/demos/button/

Spec: http://wiki.jqueryui.com/w/page/71756381/Button
yes that is correct the check is an icon so when its not checked it gets ui-icon-blank radio button does not use an icon at all it uses a span and border and just uses icon classes to keep consistent alignment.

Update: The actual icon class was originally required ( before we moved from :pseudo elements back to spans for icon ) but now that we use the position classes ( ui-icon-end etc ) that is enough with out the actual icon class so now it should be just unchecked checkboxes.