Add threshold speed setting to output files

[sarahcd]

Currently the time window setting is (# hours) is included in the app output files, but not the threshold speed setting (m/s). To keep track of results downloaded from multiple workflow runs, it would be helpful for the filenames to include both settings.

• The default threhold speed is to use the average speed for each track, rather than 1 value across all tracks, so this is not always a number.
• Adding the second setting, we need to specify which value is which.

So maybe something like "50mh_72h" for threshold speed 50 m/h, time window 72 h,
and "ave_72h_" if the average speed per track is used for the threshold.