rename phpmqtt_input.php

[emrysr]

As the phpmqtt_input service now also outputs to mqtt..

@pb66 recommended we change it in pr #905

Rename:

• phpmqtt_input.php script to emoncms_mqtt.php
• mqtt_input service to emoncms_mqtt

The documentation would also need to be updated regarding the service installation

If there are any suggestions of names please comment.

[borpin]

My concern is how to do it so it does not break existing installations.

[borpin]

This was done as part of the 9.9.6 release