FxGqlC: Added aggregation functions ENLIST and ENLISTDISTINCT

Added aggregation functions ENLIST and ENLISTDISTINCT.
ENLIST creates a string value containing the list of all string values in their original order.
ENLISTDISTINCT creates a similar list, but the dupplicate values are removed, and the list is ordered. 

SELECT [Winner], COUNT(*), ENLIST([Tournament])
   FROM ['SampleFiles/Tennis-ATP-2011.csv' -Heading=On]
   GROUP BY [Winner] ORDER BY 2 DESC
SELECT [Winner], COUNT(*), ENLISTDISTINCT([Tournament])
   FROM ['SampleFiles/Tennis-ATP-2011.csv' -Heading=On]
   GROUP BY [Winner] ORDER BY 2 DESC

This feature is added to FxGqlC in v2.5-alpha5.