Make tracks responsible for handling time manipulation
Allow setting track start and end time independantly
Better, shorter hasTime, hasElevation, getStart and getEnd implementations
If end/start has not been set, save new start/end for later
Allow editing of track times in super track table
Remove requirement to have elevation data to generate speed data
Set split times together on super track data table
Fill in lines between subtracks of super tracks
Change events to match event tree
Allow import of super tracks with JSON
Handle adding pre-populated super track
Generate speed dialog can use pre-set values from a track if it has them