New Headers for MessageId (previously GroupId)

Here is the proposal for consolidating the GroupId and SequenceNumbers elements.

 The new element in the MessageHeader would be:

 <MessageId groupId=" ">
     <SequenceNum status=" " number=" " />
 </MessageId>

 The element in PollHeader and Response would be:

 <RefToMessageIds  groupId=" ">
    <SequenceNumRange  from=" " to=" " /> * <!-- 0 or more occurrence's of this -->
 </RefToMessageIds>