Chapter 11 "Watches" - add support for transient (or non-persistent) watches

Add the following text:

The client can either 1) periodically poll the Watch URI using the pollChanges operation to obtain the events which have occurred since the last poll or 2) if the Watch was created with the makePush operation the updates will be pushed to the client as they occur as long as the connection is open.

WatchService is then composed of two operations:

<obj href="obix:WatchService">
<op name="make" in="obix:Nil" out="obix:Watch"/>
<op name="makePush" in="obix:Nil" out="obix:Watch"/>
</obj>

WatchService.makePush creates a transient watch which will be deleted on disconnection of the client.

For an Watch object which was created by this operation the existing Watch operations have following semantics:
1) Watch.add: as the existing
2) Watch.remove: as the existing
3) Watch.pollChanges: will throw an err
4) Watch.pollRefresh: will throw an err
5) Watch.delete: will throw an err