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MdSpy
stuff
Merge branch 'mdprovider_enhancements' into unpivot_stats

Conflicts:
	exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/DrillRelMdProviderSpy.java
	exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/DrillScanRelMdProvider.java
	exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/DrillTableMetadata.java
	exec/java-exec/src/test/java/org/apache/drill/exec/physical/impl/pivotstats/TestSimplePivot.java