Improve session variables to affect the query config.
 Fixed.
Completed output file rotating.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into OUTPUT_ROTATING

Conflicts:
	tajo-core/src/main/java/org/apache/tajo/engine/planner/global/GlobalPlanner.java
	tajo-core/src/main/java/org/apache/tajo/master/querymaster/Repartitioner.java
	tajo-core/src/main/java/org/apache/tajo/master/querymaster/SubQuery.java
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into OUTPUT_ROTATING
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into OUTPUT_ROTATING

Conflicts:
	tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/HashBasedColPartitionStoreExec.java
	tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/SortBasedColPartitionStoreExec.java
Added estimatedwrittensize.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into OUTPUT_ROTATING
Reflect session variables to GlobalPlanner, Repartitioner, and PhysicalPlannerImpl.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into OUTPUT_ROTATING
Reset output rotating part.
Add SessionVars and improve QueryContext.
Improved QueryContext.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-928

Conflicts:
	tajo-core/src/main/java/org/apache/tajo/master/querymaster/Repartitioner.java
Refactored QueryContext to take conf always.
Refactored TaskAttemptContext to not take TajoConf.
Fixed all unit tests.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-928

Conflicts:
	tajo-common/src/main/java/org/apache/tajo/conf/TajoConf.java
Added unit tests and refactored many classes to use SessionVars.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-928

Conflicts:
	tajo-common/src/main/java/org/apache/tajo/conf/TajoConf.java