Make NodeHashJoinPipe null safe
Tagging for version 2.1.0
Back to development version.
Update SNAPSHOT version after 2.1 release.
Merge pull request #2472 from systay/null-safe-hash-join

Make NodeHashJoinPipe null safe
Introduced a new way to write planner tests

Moved CartesianProductPlanningIntegrationTest to this new way
Moved ExpandPlanningIntegrationTest to the new planner test
Updated WithPlanningIntegrationTest
Updated LeafPlanningIntegrationTest