Gps sim

I've added a GPS Simulator that I would like included in the IO Helper.

It will simulate a GPS signal to Avare with a starting lat/long and the user can control direction, speed and altitude.  The simulator will also fly to a destination if one is set in Avare (it will even do a crude landing).  To land at the appropriate altitude there is a change required in Avare (passing back field elevation) that is not required, but I'll be making a pull request in Avare to get it.

One more thing I'd like to add eventually is the ability to input a field for starting location instead or lat/lon, but this is good enough for now.