more work on image, carousel and labelgroup

I've started work on a carousel widget, with a sample test on the imageTests.html page. Still a bunch to be done.

I improved the image widget somewhat.

I also did a little work on the labelgroup widget, changing some classes and moving some styling out of the widget code and into the widgets.css. This illustrates how I think we should be approaching things like highlighting and other widget styling.

In particular, I'd pretty much like to have NO class only selectors in widgets.css.