Replace AggregateResultSetExtractor with RowDocumentResultSetExtractor

[wool0826]

After upgrading to Spring Data JDBC 3.2.2, adopting RowDocumentResultSetExtractor for extracting ResultSets has become standard practice.

In line with these developments, we are evaluating the feasibility of switching from AggregateResultSetExtractor to RowDocumentResultSetExtractor.

If we find it's feasible, we plan to remove these classes:

• AggregateResultSetExtractor
• AggregateResultJdbcConverter