AUI-1598 - Carousel should work with text and other contents

Hi Maíra,

Attached is an update for https://issues.liferay.com/browse/AUI-1598.

Most of my changes went in image-viewer-base except for a couple small things.

1. I updated the carousel demo to show how a node can be used as content.  I pulled the design for that node from liferay.com just as an example.

2. I needed to increase the specificity of the styles for the carousel menu controls because they don't show up when used in portal.

Please let me know if there are any issues.

Thanks!