message: make getVersion methods static
diff: #define SERVER_VERSION "@VERSION_SERVER@"
  namespace aditof {
  -const std::string getApiVersion() { return std::string(ADITOF_API_VERSION); }
  -const std::string getUvcVersion() { return std::string(UVC_GADGET_VERSION); }
  -const std::string getServerVersion() { return std::string(SERVER_VERSION); }
  +static const std::string getApiVersion() { return std::string(ADITOF_API_VERSION); }
  +static const std::string getUvcVersion() { return std::string(UVC_GADGET_VERSION); }
  +static const std::string getServerVersion() { return std::string(SERVER_VERSION); }
  } // namespace aditof
  