Listen for websocket events instead of polling

[andyedinborough]

Polling is inefficient and slow. Instead, the Ryobi GDO API supports listening for events:

    public static String subscribeNotifications(String str) {
        return "{\"jsonrpc\":\"2.0\",\"method\":\"wskSubscribe\",\"params\":{\"topic\":\"" + str + ".wskAttributeUpdateNtfy\"}}";
    }

    public static String unsubscribeNotifications(String str) {
        return "{\"jsonrpc\":\"2.0\",\"method\":\"wskUnsubscribe\",\"params\":{\"topic\":\"" + str + ".wskAttributeUpdateNtfy\"}}";
    }

We should update the code to open the websocket on start and keep it open with periodic pings.