DRILL-316: check return type for function resolution. delete two un-needed test json files.
Drill-316: code change for review comment 1 and 2.
Drill-316: address review comment 3.
Drill-316: address testcase comments.
Drill-316: Decode byte array directly into int/long, when cast varchar/varbinary into int/bigint.
Drill-316: minor change to grammer rule for cast.