Added MQTT client, better speaker handling, fixed bug in FTP server, ...

lib/pubsubclient/README.md

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+# Arduino Client for MQTT
+
+This library provides a client for doing simple publish/subscribe messaging with
+a server that supports MQTT.
+
+## Examples
+
+The library comes with a number of example sketches. See File > Examples > PubSubClient
+within the Arduino application.
+
+Full API documentation is available here: https://pubsubclient.knolleary.net
+
+## Limitations
+
+ - It can only publish QoS 0 messages. It can subscribe at QoS 0 or QoS 1.
+ - The maximum message size, including header, is **128 bytes** by default. This
+   is configurable via `MQTT_MAX_PACKET_SIZE` in `PubSubClient.h`.
+ - The keepalive interval is set to 15 seconds by default. This is configurable
+   via `MQTT_KEEPALIVE` in `PubSubClient.h`.
+ - The client uses MQTT 3.1.1 by default. It can be changed to use MQTT 3.1 by
+   changing value of `MQTT_VERSION` in `PubSubClient.h`.
+
+
+## Compatible Hardware
+
+The library uses the Arduino Ethernet Client api for interacting with the
+underlying network hardware. This means it Just Works with a growing number of
+boards and shields, including:
+
+ - Arduino Ethernet
+ - Arduino Ethernet Shield
+ - Arduino YUN – use the included `YunClient` in place of `EthernetClient`, and
+   be sure to do a `Bridge.begin()` first
+ - Arduino WiFi Shield - if you want to send packets > 90 bytes with this shield,
+   enable the `MQTT_MAX_TRANSFER_SIZE` define in `PubSubClient.h`.
+ - Sparkfun WiFly Shield – [library](https://github.com/dpslwk/WiFly)
+ - TI CC3000 WiFi - [library](https://github.com/sparkfun/SFE_CC3000_Library)
+ - Intel Galileo/Edison
+ - ESP8266
+ - ESP32
+
+The library cannot currently be used with hardware based on the ENC28J60 chip –
+such as the Nanode or the Nuelectronics Ethernet Shield. For those, there is an
+[alternative library](https://github.com/njh/NanodeMQTT) available.
+
+## License
+
+This code is released under the MIT License.