DRILL-6834: Introduce option to disable result set for DDL queries for JDBC connection
- Added session-scoped option `drill.exec.fetch_resultset_for_ddl` to control whether update count or result set should be returned for JDBC connection session. By default the option is set to `true` which ensures that result set is returned;
- Updated Drill JDBC: `DrillCursor` and `DrillStatement` to achieve desired behaviour.
closes #1549
