v2.7.2

• [Client] Added the subprotocol "mqtt" as default for web socket based connections.
• [Client] Added a new client setting called "KeepAliveSendInterval". It allows configuring the effective interval for sending ping requests.
• [Client] The client will no longer send ping requests if other packets are sent within the configured interval.
• [Server] The server now generates a valid packet identifier when disaptching publish packets to clients.
• [Core] Add several new extension methods.