[Telepathy] On spec additions to allow a really simple IM API

[Will Thompson]

For the record: Vivek is currently working on implementing André's
suggested ChannelDispatcher interface, on the basis that this involves
the fewest modifications to the fewest components. (With a few tweaks
compared to Olli's original mail on the subject, such as not magically
transforming Create calls into Ensure calls. I'll leave it to him to
outline how it'll work.)

If it turns out to do the trick, great; if he finds unforeseen problems
with that approach, we can reconsider adding more API to CMs.

-- 
Will