the current method works when steering_angle is 0

when steering is <> 0, then heading is changing (as well as position)

first calc the new heading

then calc the new position (already done)

treat steering_angle as a bearing, that is, an angle in degrees, add it to the previous heading to get the new heading

  lastKnownHeading + steering_angle = newHeading

     heading = orientation of the vehicle 

      heading+helm = prediction of future course

      course = actual travel = line from previous position to current position

      simmode = precise
              heading is set instantly to what we want we want it to be
              line: heading = course, line from prevpos to current positon
              arc: heading is assumed to be perpendicular to the ray from cone to current position
              both: on nextleg, heading jumps to next leg from
              no drift

      simmode = helmed
              heading is what it is
              course is what it is
              set helm bring course back to what we want              
              includes drift

      when we reach a cone
              change bearing to next cone
              set helm to steer a circle - how to calculate this based on radius and speed?
              stay in the circle until heading = bearing