* That's a lot of XML errors. Sorry.
* Clarified whose additional-data this is.
* <:next> uses <initial-response>.
* Added a bunch of example flows.
Updated according to implementation experience:
* Updated namespace
* Continue "mechanisms" are not; changed these to "tasks".
* Added stream features after Success.
* Don't need complexity of "=" encoding; removed.
* Fixed internal links.
* Updated examples.
