Prepare repository for setting public

[MaxBaex]

• Add GPL3 headers with our project name to own source files.
• Provide a short markdown manual for how to configure a sensor via the sd-card parameter file:
  • What is important when mounting the sensor into the airplane
  • Mount orientation
  • GNSS variant
  • Magnetic Variation / Declination. The manual shall explain if the pilot must reconfigure the variation values in case the airplane travels e.g. to south africa, australia , ..