improve the image toggling in TESTSUITE

At http://localhost:8080/site/newsimagevariant/2009/01/launch-cms-7.html you can toggle the image at the bottom.

There are sloppy parts in it:

1) The original image is loaded even when not yet displayed
2) The javascript is not added as head contribution
3) The javascript is non namespaced, hence, easily leads to function collisions