Add field functions: Misc

[fidian]

• Glide Ratio (ratio)
• Heading (direction)
• Odometer (distance)
• Relative bearing (direction, to dest)
• Velocity Made Good (speed, to dest)
• Vertical Speed (speed)

[fidian]

Heading is done, giving the device's heading and the smoothed heading as options.

Odometer is done and it shows up as "Distance Traveled".