Add an "htmlStyle" attribute to Label and other places

It would be really cool to be able to apply some of the HTML style tags (such as <b>, <i>, <sup>, etc.) to text inside a Label. Then by extension things like Button.DataRenderer could inherit the same things. That way you could create buttons with interestingly styled text without having to create a bitmap.

It's a lot of work inside LabelSkin but it would translate easily to other places that use Labels for rendering.