Add Laps section to the Activity page

[david]

Laps and interval detection updates

A couple of important changes as to how intervals are detected: All laps are kept when detecting intervals from lap data. Before intervals with low power, HR or pace were removed. Lap data is now used for power based intervals for structured workouts done on Garmin devices. Intervals are labelled according to the workout step they are for (if any). Note this does not work with activities from Strava. You need to be using Garmin Connect integration, upload fit files manually or use Dropbox. […