- Filter the fuel switch position to allow it to slowly transition through

- Filter the fuel switch position to allow it to slowly transition through
  null space without killing the engine (hardware specific problem.)
- NMEA output: I'm slightly confused but it appears that a real GPS outputs
  traditional unix line endings on it's gps strings, we were outputing DOS
  CR/LF which was causing some confusion.  This changes the line ending
  convention to match that of a real gps.
- Calculate true ground track and speed for NMEA.