Include global cloud fraction, DNI, DHI in feature file

[amcmahon01]

Current cloud fraction values are for feature point windows only (i.e. 100x100 px at feature point). Full sky cloud fraction should be calculated and included, along with DNI and DHI values.

[amcmahon01]

This is likely preventing the 5% overcast/clear thresholds from doing anything useful since they're only integrating tiny windows and likely making forecasts considerably worse. The current "feature" cloud fraction values should still be included however.