mark-p-thomas : Track Stats

While any polyline segment has some concept of a length, tracks are actual paths in the real world that occur over time. As such, these include additional stats such as time, speed, and height rate. Height rate is further signed in case a user only wants stats that apply to ascending or descending movement. Implementing or referencing the IRangeStatsResult interface allows each route criteria to include a broad range of stats.

Each Track stat is a higher-level concept that includes a suite of lower-level stats, such as sum, mean, median, max/min, standard deviations, and ranges.