pull request to integrate changes into the GUI experimenter interface

note that this entails changes in iat.js and index0 that change the behavior from the previous versions. In other words, this version behaves differently from the previous ones: it does not offer to enter a subID manually, and it always tries to jump to the nextURL in the end. I guess it makes sense to create a version that can behave flexibly and accomodate both kinds of behaviors, stand alone and embedded, but that needs further editing of my changes.