move to c++17, change message building, refactored SensorInformation and MeasurementData

- messages are now built using the constructor
- messages now only contain a single measurement value, even if a sensor might include more than one measurement
- buildMessage has been changed to buildMessages and now returns a list of messages depending on how many measurements a sensor contains
- ClientDataPackage now builds from SensorInformation and MeasurementData
- minor naming refactors