Add "Clear Intervals" to Edit menu (activities list)

Since activities must have either laps from device or detected intervals (unfortunately we can’t have none), it would be very useful to have a bulk “Clear Intervals” option in the Activities List.

“Clear Intervals” is an action already avaliable at the Actions menu (on a activity).

Sometimes we end up with a large number of activities with automatically detected intervals, resulting in those “skyline” graphs that don’t make much sense in the calendar. Having a bulk option would make it much easier to clean these up.