Simplified State Management

1) Update the CONNECT packet variable header to replace the Clean Session flag with a Clean Start flag in the same position in the Connect flags. Clean Session is renamed to Clean Start. If set to 1 this causes any existing Session State to be deleted on CONNECT but not on DISCONNECT. Consequently the Session Present flag in CONNACK is always set to 0 if Clean Start is set to 1 on CONNECT. This bit specifies whether the Session state is deleted when a connection is made. Jira 249 - Session State Expiry interval contains the definition of the Session State. Non normative comment To ensure consistent state in the event of a failure during connect, where SessionPresent=1, is unexpectedly received, the Client should repeat its attempts to connect with a Clean Start set to 1, until it connects successfully. Non Normative comment Setting a Session Expiry interval of 0 and Clean Start to 1, is equivalent to setting Clean Session to 1 in the MQTT Specification Version 3.1.1. Setting no Session Expiry interval and setting Clean Start to 0 is equivalent to setting Clean Session to 0 in the MQTT Specification Version 3.1.1.