Updated documentation for knx component. (home-assistant#3685)

* Updated documentation for knx component. Added option for configurable state updater.

* Minor changes

source/_components/knx.markdown

@@ -76,10 +76,10 @@ knx:
     fire_event_filter: ["1/0/*", "6/2,3,4-6/*"]
 ```
 
-* **fire_event** (Optional) if set to True, platform will write all received KNX messages to event bus
-* **fire_event_filter** If `fire_event` is set `fire_event_filter` has to be specified. `fire_event_filter` defines a list of patterns for filtering KNX addresses. Only telegrams which match this pattern are sent to the HASS event bus. 
-
+* **fire_event** (*Optional*): If set to True, platform will write all received KNX messages to event bus
+* **fire_event_filter** (*Optional*): If `fire_event` is set `fire_event_filter` has to be specified. `fire_event_filter` defines a list of patterns for filtering KNX addresses. Only telegrams which match this pattern are sent to the HASS event bus. 
 
+* **state_updater** (*Optional*): The component will collect the current state of each configured device from the KNX bus to display it correctly within Home-Assistant. Set this option to False to prevent this behaviour.
 
 Service
 -------
@@ -92,8 +92,8 @@ Service: send
 Service Data: {"address": "1/0/15", "payload": 0}
 ```
 
-* **address** : KNX group address
-* **payload** : payload, either an integer or an array of integers
+* **address**: KNX group address
+* **payload**: Payload, either an integer or an array of integers