Calibration problem

[cdupont]

Currently, when a calibration is present in the "sensor" datastructure, this calibration will be used to calculate the values output by the API (e.g. in devices/XX/sensors/YY/values).
This will cause problems because the "value/values" fields of a sensor changes meaning.
For instance the synchronisation module in the gateways will think this is the raw value, while this might be the calibrated value.

[cdupont]

Proposed change:

• add value_calibrated field in the sensor datastructure. This read-only, optional field will contain the calibrated values, when there is a calibration.
• The existing value field will contain the raw value (instead of raw/calibrated) in read-write mode.

Having two fields allows to avoid confusion. There should be no changes on the gateway side. On the dashboard side, I think it is better to display the calibrated value, when it is available.

[cdupont]

@j-forster