Overhaul webapp meta properties and JavaScript API to reflect new windowing code

With the recent update to the windowing code, many of the properties exposed to webapps and the JavaScript API have become invalidated. Similarily many new properties are ripe for exposing new functionality or finer grain control over existing functionality. I have already, as far as possible, tried to harmonise the existing properties in such a way as to offer similar effects to what they did before the change. However, I am of the opinion that we would be better just start from scratch and expose an entirely new set of much lower-level / finer-grain properties that accurately match the underlying code. This would of course break the existing sample applications that have been produced, but the benefits of updating these applications outweigh the workload, in my opinion.