progress on the image widget(s)

Just think it's time to merge these back in.
I've got an Image widget and a CaptionedImage widget working.
There's a test in imageTests.html, the caption isn't in exactly the same place as before, and I think it will need more work anyway, but the framework seems reasonable, take a look at the test.

Next will be the ImageCarousel widget, or perhaps just a Carousel widget.