Support concept2 details file

[kumlien]

When using file based sync: it should be possible to drop a file with details on a synced activity. The activity should then get updated with distance and heartbeats if available.
No, sorry but RunKeeper only allow for updating the heart beat rates, not the distances...

[kumlien]

Would be nice with

1. Right-click on a row
2. Choose "add stroke data" or something
3. Present a file chooser
4. Press ok, and the rk activity is updated.

[kumlien]

• Add context menu to the grid (Nope, context menu on grid is not trivial, use button instead)
• Create form for choosing the file
• Parse the csv file
• Update the distance and heartRate (if available) for the activity