Implement sensor status debouncing

This introduces a configurable debouncing delay before which no update
is sent to matrix, which avoids flooding the matrix room with updates
when the door is opened and closed in quick succession. It also allows
to quickly open and close the door without sending notifications.

The debouncing window can be configured in config.yml, see example.

config.yml.example

@@ -9,6 +9,8 @@ mqtt:
 rooms:
   - "!iFCnqQcvrVIeehrjQO:chat.labolyon.fr"
 
+debounce_delay: 10 # seconds
+
 # username / password login
 # /!\ will create a new device every time the bot starts
 username: "login"