Add extra information

[albfan]

Use case: I just run a triathlon and I loose my chip at very beggining. In the end, organization only register start and end time (classification)

I wear gps watch and cyclocomputer so I have exact tracks for all the run.

The thing is a triathlon tracks should not only cover swing, bycicle and run but transitions. In order to extract that data:

• Gpx graph needs to show time for each point (done but DateTime.to_local() do not counts correctly summer time)
• Gpx graph should show partial time from beginning
• Rename tracks
• cut tracks (for transition)

[albfan]

I will provide a patch for all this. I have it working locally