MQTT ready to use

change subscription logic - now keep subscriptions independently from connecting state. No unregisters on disconnect, but resubscriptions on connect. So one-time subscription on app start and just connect() on lost connection - all subscriptions keeps

libs/main/mqtt_client/pimqttclient.h

@@ -50,7 +50,6 @@ public:
 	void connect(const PIString & address, const PIString & client, const PIString & username = {}, const PIString & password = {});
 	void disconnect();
 
-
 	void subscribe(const PIString & topic, MessageFunction functor, QoS qos = QoS::Level1);
 
 	template<typename T>
@@ -68,6 +67,8 @@ public:
 	bool isConnecting() const { return m_status == Connecting; }
 	bool isConnected() const { return m_status == Connected; }
 
+	PIStringList usedTopics() const;
+
 	EVENT0(connected);
 	EVENT1(disconnected, PIMQTT::Error, code);
 	EVENT1(receivedUnhandled, PIMQTT::MessageConst, message);