The main motivation is to allow users to set the per-partition number
of rows for manual incremental stats maintenance, as well as a means
to 'drop' stats that may have caused undesirable plan changes.
Change-Id: Iff38317a993e5d7952ea4df839947f5ec341e930
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1010
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: jenkins