Major technical suggestion

[Rich Salz <rsalz@caveosystems.com>]

I suggest that inter-MSH messages -- e.g., ping, pong, and any delivery
acks/nacks we define -- be actual ebXML messages where the From and To
Parties are the MSH's themselves. The message is moved OUT of the
ebXMLHeader document, and becomes its own document in the payload.

This seems to be much simpler and cleaner.  It also lets us move them
off the main track.

Apologies is this was already considered and rejected.
	/r$