item plugin conf: prec value is ignored from config file

[karel-rehor]

related to #6

---yaml
broker:
  host: "localhost"
  port: 1883
  auth:
    username: "fred"
    password: "changeit"
devices:
- id: "random"
  name: "accelTestDevice"
  description: "testing accelerator plugin"
  samples:
  - name: "accelTestSample"
    id: "random"
    topic: "test/accel"
    items:
    - name: "speed"
      label: "speed"
      type: "Plugin"
      pluginName: "AcceleratorPlugin"
      resultType: "Double"
      prec: 3
  interval: 500
  jitter: 100
  count: 3
ttl: 10000

run with

java -Drunner.conf=plugins/examples/accelerator/sampleRunnerConfig.yml -jar target/virtual-device-0.1-SNAPSHOT-8c36a7e.jar 

from listener

Callback on publish MqttPublish{topic=test/accel, payload=118byte, qos=AT_MOST_ONCE, retain=false}
Payload {
  "id" : "531a8eb4-6c6e-4a36-83ca-30586ba806e7-001",
  "timestamp" : 1685364020473,
  "speed" : 31.294118694885583
}
Callback on publish MqttPublish{topic=test/accel, payload=118byte, qos=AT_MOST_ONCE, retain=false}
Payload {
  "id" : "531a8eb4-6c6e-4a36-83ca-30586ba806e7-003",
  "timestamp" : 1685364020474,
  "speed" : 58.081942774582416
}