Fast Best and TIZ queries

Added static functions to ridefilecache
to get best and tiz values for series and duration
or zones and glued them in to the datafilter code
recently added.

It uses seek (via QDataStream::skipRawData) and is
quite fast on my Linux development PC.

We now need to update the LTM settings dialogs to
the new mockups so we can plot custom durations for
peak power / NP etc too.

NOTE: Not tried on Windows / Mac, so may not be quite
      so fast there, will need to check.

      To try this out, in the search filter box type:

            best(power, 3600) > 250

      to filter only those rides where the best hour
      power is greater than 250 watts. It should
      return almost instantly.