Add sorely lacking disable() and enable() functions to jQuery

jquery.disable.js

(function ($) {
	$.fn.disable = function () {
		return this.each(function () {
			$(this).attr("disabled", "disabled");
		});
	}
	$.fn.enable = function () {
		return this.each(function () {
			$(this).removeAttr("disabled");
		});
	}
})(jQuery);