modify module for measurement plot for external sensors
add module for post
modifiy prototype for external sensors and error handling of communcation errors of VNA
add regresson to post plot with basich control elements

- Load VNA config (and calibration) from file.
  The *.znxml file has to be prepared in advance and saved on the VNA.
  It needs to set the VNA to CW mode and single sweep.
- Trigger single sweep and wait for it to complete
- Fix trace definitions

- Frequency is a new parameter in json file
- Set wide acceptance ranges of other test stand parameters for demo purposes