====== Pulse count ======

Pule counting should support :
  * Hall sensor
  * Optical sensor
  * Third party sensor like Itron cyble

Features :
  * The node will send the total pulse count every time it encounter a pulse (never less than once per 10 sec and never more than once per 2 sec).
  * At startup, the node will ask the gateway for the last value sent (offset).