* implemented distinct
* implemented distinct
* uses first cut of a buffer pool, and extendible hashing with thresholded spill to disk
* tests
* cleaned up some stuff around query plan output to make developing tooling easier
* added optimization to call PQL Distinct()
* fixed test
* fix for passing wrong index name in orchestrator
* back out change to DistinctTimestamp
* fix other instance of wrong table name being passed
* use full index name instead of abbreviated one for translation. sigh.
* removed some unused code
Co-authored-by: Matthew Jaffee <jaffee@pilosa.com>
(cherry picked from commit f030d58d95)
