MQTT notificator

[albinpllanaa]

Hi
I have been working on supporting MQTT notifications on Traccar using Eclipse Paho client.
MQTT is a lightweight publish-subscribe messaging protocol and it can be used also for Push Notifications on mobile apps.
Keys to configure the MQTT:

<entry key="notificator.mqtt.server.url">tcp://localhost:1883</entry>
<entry key="notificator.mqtt.client.id">traccar</entry>
<entry key="notificator.mqtt.username"></entry>
<entry key="notificator.mqtt.password"></entry>

First two keys are required, and the last two keys are needed only if MQTT server is secured with username and password.

Please review the changes and provide your feedback. Thank you!

Best regards