[DP-89] Strenghen the ordering guarantees in distributed-process

[qnikst]

[Imported from JIRA. Reported by jwaldmann @jwaldmann) as DP-89 on 2014-03-11 08:51:05]
A "channel" can be one of many things, and the API docs don't say what's happening:

• does it have a capacity? (can it store messages?)
• if yes, what guarantees are there for message ordering? (is it FIFO in some concurrent sense, that is FIFO between a fixed pair of sender and receiver process?)

and the same for send/expect - with the extra difficulty that the underlying channel is untyped? What does this imply for message ordering (e.g., FIFO-by-type)?

You have some "INTERNAL NOTES" in C.D.Process - please make them visible in the Haddocks.

[hyperthunk]

I think all these are spelled out in the docs, the semantics, and the website. @qnikst do you think we need to explain things further?