Generic messaging updates

Extend MessagingIRI to support replacing EmailIRI,
and for other generic messaging systems.

Extend Messaging-System-Type with:
	undefined(0), smtp(2), pop3(3), imap4(4),
	webmail(5), mms(6), rcs(7), sms(8)

Extend Messaging-Event with:
	partial-retrieve(8)

Extend Messaging-Box-Event with:
	start-of-interception-with-session-active(32)
	end-of-interception-with-session-active(33)

Extend Messaging-Party-Validity with:
	rejected(3)

Extend Messaging-Property with:
	server-octets-sent
	client-octets-sent