No more UploadedTo, replaced with ServiceData/ServiceDataCollection
RK stationary activity stuff
Added SportTracks statistics, changed Stats.Distance/MovingTime/Distance to use ActivityStatistic
Activity statistic coalescing + tests for that & unit conversions
Coalesce activity statistics when accumulating activities, misc cleanup
TCX stationary statistic export.
Added support for GPXDATA extensions for cadence/HR in addition to GPXTPX for GPX ingest.
Fixed improper usage exception when Endomondo activity download threw APIExcludeActivity during activity list without providing ExternalActivityID