Add device availability functionality for HASS based on router devices ping and attribute reporting also available on battery-powered devices (#761)

* Discovery on HASS restart and last_message attribute added

- On restarting Home Assistant, resending device discovery information
- Add timestamp on receiving message from Zigbee

* Add option: add_timestamp in settings

* typo

* Update homeassistant.js

* Update homeassistant.js

* Update homeassistant.js

* Update controller.js

* Update zigbee.js

* Add files via upload

* Update zigbee.js

* Update deviceAvailabilityHandler.js

* Update deviceAvailabilityHandler.js

* Update deviceAvailabilityHandler.js

* Update deviceAvailabilityHandler.js

* Update deviceAvailabilityHandler.js

* Update deviceAvailabilityHandler.js

* Update deviceAvailabilityHandler.js

* Update homeassistant.js

* Update deviceAvailabilityHandler.js

* Update deviceAvailabilityHandler.js

* Update homeassistant.js

* Fix checkonline callback.

* Refactor.

* Refactor.

lib/controller.js

@@ -17,6 +17,7 @@ const ExtensionDeviceReceive = require('./extension/deviceReceive');
 const ExtensionMarkOnlineXiaomi = require('./extension/markOnlineXiaomi');
 const ExtensionBridgeConfig = require('./extension/bridgeConfig');
 const ExtensionGroups = require('./extension/groups');
+const DeviceAvailability = require('./extension/deviceAvailability');
 
 class Controller {
     constructor() {
@@ -53,6 +54,12 @@ class Controller {
                 this.zigbee, this.mqtt, this.state, this.publishDeviceState
             ));
         }
+
+        if (settings.get().experimental.availablility_timeout) {
+            this.extensions.push(new DeviceAvailability(
+                this.zigbee, this.mqtt, this.state, this.publishDeviceState
+            ));
+        }
     }
 
     onMQTTConnected() {