More WPK interval SEGV fixing

.. in interval summary
.. and workout wizard

There aren't any other computeMetrics() pieces of code
left. I also scanned for new RideFile() code and it was
limited to the RideFileReaders which are managed by the
openRideFile() base method, so all should now be well.
Merge branch 'master' of github.com:/GoldenCheetah/GoldenCheetah