Session Initialization Clarification with datagrams

[TimEvens]

Section 3.3 states "The first stream opened is a client-initiated bidirectional control stream where the peers exchange Setup messages (Section 6.2)" but does not state what we should do about datagrams being sent before the control stream as well as before CLIENT_SETUP/SERVER_SETUP.

Should the connection be closed by protocol violation if DATAGRAM is received matching any of the following conditions:

• Control bi-dir stream not yet created; session hasn't been established
• CLIENT_SETUP and SERVER_SETUP not compete; session hasn't been established
• CLIENT_SETUP role is 0x02 SUBSCRIBER; publishing is not allowed

[ianswett]

If you get a Datagram or Unidirectional stream with Objects from a subscription or Fetch you've never made, then it's a protocol violation.

@TimEvens can you write a PR to this effect?