[DPP-54] Control.Distributed.Process.Platform.Task

[hyperthunk]

[Imported from JIRA. Reported by Tim Watson [Administrator] @hyperthunk) as DPP-54 on 2013-01-12 18:02:26]
Building on the facilities available in Control.Distributed.Process.Platform.Async, it would be good to be able to pass a handle to an Async to another process or send it to another node. That's currently impossible because we use typed channels and STM in the two Async implementations, so we'll need a central server to track the task state. This will open up lots other possibilities, including sharing async results with multiple consumers and using task pools of varying configurations to create async processing units.