TWP/SKYRAD/C2 - Reprocess: PIR identified as unshaded is really shaded

On 17Sep01 the Global PIR was moved from the unshaded position
on the Skyrad stand to the new 'shaded' spot on the new K&Z tracker.
It is still using the same Logger channel as it did as an unshaded 
PIR even though it is now shaded.

The unshaded PIR is now a shaded PIR.  Disregard the data description
in the netcdf header

• Downwelling Longwave Hemispheric Irradiance, Unshaded Pyrgeometer, Maxima(down_long_hemisp_unshaded_max)
• Downwelling Longwave Hemispheric Irradiance, Unshaded Pyrgeometer, Standard
  Deviation(down_long_hemisp_unshaded_std)
• Downwelling Longwave Hemispheric Irradiance, Unshaded Pyrgeometer, Minima(down_long_hemisp_unshaded_min)
• Downwelling Longwave Hemispheric Irradiance, Unshaded Pyrgeometer(down_long_hemisp_unshaded)