RideCache / RideItem fixups

.. fingerprint for range should not take into account the
   start/end date as its irrelevant and will change

.. RideItem now responsible for refresh and status updating
   on the rideitem

.. framework seems good now; only rides that need to be refreshed
   will get asked for a refresh -- but need to look more closely
   at how we derive 'Weight' for each rideitem now...