Implement MQTT events

[Sholofly]

Second attempt to implement an eventlistener based on MQTT.

How to use?
After creating the fully kiosk class call the start() function with a parameter callback function:

def on_event_callback(event_type:str):
    print(event_type)
    # For example: Pass function for sensor refresh here when event_type == deviceInfo
    # event_type: deviceInfo updates the device info in the api, so technically you don't need to call the getDeviceClass 
    # seperately anymore

session = ClientSession()
api = FullyKiosk(session, "<host-ip>", <port>, '<admin-password>')`
await api.start(mqtt_event_callback=on_event_callback)

[Sholofly]

@cgarwood Do you mind to take a look?