[SPARK-9830][SQL] Remove AggregateExpression1 and Aggregate Operator used to
evaluate AggregateExpression1s
https://issues.apache.org/jira/browse/SPARK-9830
This PR contains the following main changes.
* Removing `AggregateExpression1`.
* Removing `Aggregate` operator, which is used to evaluate
[SPARK-9830][SQL] Remove AggregateExpression1 and Aggregate Operator used to
evaluate AggregateExpression1s
https://issues.apache.org/jira/browse/SPARK-9830
This PR contains the following main changes.
* Removing `AggregateExpression1`.
* Removing `Aggregate` operator, which is used to evaluate