Make client-side redirect behavior configurable for Ajax requests

Web flow always requests a client redirect when transitioning to a new view — even if its being called from an ajax client.... the only time a redirect is avoided is when the view-state doesn't change e.g. re-rendering a fragment in the same view.

It should be possible for a flow to be fully contained within a zone on the page and be called into fully asynchronously like the shipping-rate sample in swf 1.x. In this case, having that flow issue a client-side redirect is not necessary. The flow should detect it is operating inside a nested part of the page and is not the controller for the entire page.