Add support for MQTT Integration

[apoc4lyps]

Add Support for Octoprint MQTT Integration in addition to the Octoprint API (https://plugins.octoprint.org/plugins/homeassistant/)

[dangreco]

I've looked over the implementation and it looks good -- thanks! However, quick question from someone who doesn't use OctoPrint via MQTT: are the entity ID suffixes for OctoPrint x MQTT the same for every user? Or would they have to configure their MQTT sensors to match the format specified in the code?

[Jan-Ka]

Entity ID suffixes from OctoPrint-HomeAssistant are static (i.e. same for every user) as they are read through MQTT Discovery.

Example Print Status: https://github.com/cmroche/OctoPrint-HomeAssistant/blob/5a8afe732671e7eb40c41ea6051c52caec6e0094/octoprint_homeassistant/__init__.py#L249

Pretty sure, without altering the Plugin Implementation, there's no easy way to change these.

[dangreco]

Merged! Thanks again guys!!