Add test mode flags to AbstractPlanNode/AbstractExpression for more detailed explain.
Merge pull request #1064 from VoltDB/explain-debug-mode

Add test mode flags to AbstractPlanNode/AbstractExpression for more detailed explain
ENG-5527,ENG-5526,ENG-5525: Tie pro-ness and error message to StartAction instance.
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Merge remote-tracking branch 'origin/master' into it18grabbag