Add headers, to appease the RAT.
[CALCITE-467] Incorrect namespace in package-info.java
Initial commit
Multiple aggregations support
Better count(*) support
Checkpoint
Very basic support for nested types using x['y'] notation.
Update to Calcite from Optiq
Force use of ElasticsearchProjectRel

Trivial projections were not getting pushed into
ElasticsearchProjectRel due to a Volcano rule called ProjectRemoveRule.
Manually removed this.
Working on interpreter-based enumeration
Adding interpreter tests