Duration is missing in HomeKit for valves

[AndreasPrang]

I think for water valve the following Characteristic is missing to have duration variable working properly:

.getCharacteristic(Characteristic.RemainingDuration)

[AndreasPrang]

I realised it with like this:

  sprinkler
  .getService(Service.Valve)
  .getCharacteristic(Characteristic.RemainingDuration)
  .on('get', function(callback) {

    var err = null; // in case there were any problems

    if (SPRINKLER.active) {

      var duration = SPRINKLER.timerEnd - Math.floor(new Date() / 1000);
      console.log(SPRINKLER.typeName + " RemainingDuration: " + duration)
      callback(err, duration);
    }
    else {
      callback(err, 0);
    }
  });

[AndreasPrang]

Fixed the issue with PR #88