Short track smoothing

[brandonwkerns]

When LPT systems are less than 5 time stamps in length, spline smoothing to generate "centroid_lon_smoothed" will fail, and the script will crash.

[brandonwkerns]

Proposed solutions:

• Turn off smoothed track. Just return the original track as the smoothed track.
• Polynomial fits for less than five points.

[brandonwkerns]

Could use linear interpolation, which would fill in gaps when there is a center jump.