Add csv columns for criteria even if datasets are empty
Add csv columns for criteria even if datasets are empty

If one of the datasets was empty for a 'harpcollocate matchup' then the resulting collocation result file did not have columns for the provided criteria. This is now corrected.

stcorp/harp,stcorp/harp,stcorp/harp,stcorp/harp,stcorp/harp,stcorp/harp