[Control Protocol] Cross reference control protocol messages with Presentation API steps

[markafoltz]

The steps in the Presentation API spec that require communication between the controlling and presenting user agent should be cross referenced with messages in the Presentation API control protocol.

Related to this, there are implicit dependencies between messages: i.e. the Termination Request can't be sent before the Initiation Request for a given presentation. These should be made explicit through sequence diagrams showing how messages relate to the lifetime of a presentation or a presentation connection.