DRILL-3285: Part 1--Prep., Hygiene: Mainly, adding comments.
Added/edited comments:
- field doc. comments
- method doc. comments
- branch/block comments
Removed unused recordBatchCount and getRecordBatchCount().
Added logger call for spurious batch.
Various cleanup:
- Cleaned up logger.
- Added "final" on updateColumns().
- Wrapped some lines
- Misc. comment whitespace.
