Disable client window through parameter

When exiting a flow, I sometimes need to redirect the user to some page where the client window id is not relevant anymore. It would be nice if the jfwid parameter could be dropped by simply adding "disable-client-window=true" in the url.

```
flowBuilder.returnNode("returnFromFlow").fromOutcome("/index.xhtml?faces-redirect=true&disable-client-window=true");
```

Start by tracing how the flowBuilder.returnNode("returnFromFlow").fromOutcome(...) entry point handles the jfwid parameter and URL query parameters. Check the related tests, if present, and verify that adding disable-client-window=true to the example URL prevents jfwid from being retained when leaving the flow.

Written by the indexing model from the issue text.