Bugfix - client is locked when receiving QoS2 messages

Removed the spurious locks when receiving QoS2 messages causing the client to halt.

First release

• MQTT 3.1.1 compliant library
• Sending and receiving at all QoS levels
• TCP and TCP/TLS using standard WiFiClient and WiFiClientSecure connections
• Virtually unlimited incoming and outgoing payload sizes
• Readable and understandable code
• No dependencies outside the Arduino framework

Full documentation at https://bert.emelis.net/espMqttClient

Multisub/multiunsub

You can now subscribe to multiple topics using only 1 message.
Same goes for unsubscribe.

Chunked payloads

It's now possible to publish large payloads. Instead of adding the payload during publishing, a callback has to be passed.

When actually publishing, the callback is used to fetch payload data. Be aware that the same payload data can be fetched multiple times to be able to honor the different QoS levels.

Fix removal of PUBACK and PUBCOMP

puback and pubcomp are 'final' packets. Once they have been sent, they can be deleted from the queue.

Bugfix: queue clearing

• The outgoing queue wasn't cleared correctly resulting in protocol errors
• Headers for unsecure and secure client have been merged (code deduplication)
• Some unit tests have been added

Emplace in queue

• emplace packets in queue
• disconnect improved

Bugfix unsub packet

unsubscribe packet was not being acknowledged. cppcheck revealed the issue

printf warnings have been fixed

v0.0.4

Documentation added

• a small detail: removed the possibility to call loop() on ESP32. We don't want to have it running simultaneously in two tasks.

Bugfix - set DUP flag when needed

After completely sending a message, the DUP flag is set on PUBLISH messages with QoS > 0. So when the connection drops and a re-delivery is attempted, the DUP flag is set as it should be.