Added a headwind data field, which is available when using
an iAero head unit, to dramatically improve the calculation
of Chung analysis for users of more recent iAero devices.
All other data files than the iAero have the headwind term set to
zero when they append a point.
RideFile data points now include lon and lat members for the longitude
degrees and latitute degrees from the source ride files. As a result
most of the RideFile readers now set longitude and latitude to zero for
each data point, except for:
* Gc Format Files - now support read/write
* Wko Format Files - now support read
* Tcx Format Files - now support read (smoothed if smart recording)
Although there are no features within GC at this point in time that use
positioning data this may change over time. Critically, as users save
files to the new GC file format whilst adding interval data it is
important that this positioning data is not discarded before new
features arrive.
