Changes in hedwig client api to support JMS spec

Primary changes are :

a) Add support for returning seq-id for a publish request. This is an api change (backwardly compatible for users).
b) Make consume a sync consume, with addition of an asyncConsume - this is to ensure that invoking consume() ensure request makes to server before returning (with what reasonable gaurantees that netty allows).
c) Ensure that explicit close'ing of session will flush buffered consume seq-id's when auto-ack is enabled (default in hedwig java client).

In addition, there are also fixes for
d) Fix NPE's observed as part of testing JMS provider.