Apply new aggregation functions for datastream and dataset tables
1. Change the implementation of the DataStream aggregation runtime code to use new aggregation functions and aggregate dataStream API.
2. DataStream will be always running in incremental mode, as explained in 06/Feb/2017 in FLINK5564.
2. Change the implementation of the Dataset aggregation runtime code to use new aggregation functions.
3. Clean up unused class and method.