Demos: removed superfluous class from selects examples.
Select: Remove class ui-btn-left/right from the select element itself during enhancement. Fixes #5073
Prevent margin top/bottom on selects, checkboxes and radio buttons with class ui-btn-left/right.
Demos: added ungrouped radio buttons example.
Checkboxradio: No need to set margin for the buttons because we already set it for .ui-btn and .ui-btn-mini. Repeating it makes it only more difficult to override when needed.