TAJO-96: Design and implement rewrite rule interface and the rewrite rule engine. (hyunsik)
TAJO-102: Add AlgebraVisitor and Refactor LogicalPlanner to use the visitor. (hyunsik)
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-tajo into Improve_Optimizer

Conflicts:
	tajo-core/tajo-core-backend/src/main/java/org/apache/tajo/engine/planner/LogicalOptimizer.java
	tajo-core/tajo-core-backend/src/main/java/org/apache/tajo/engine/planner/LogicalPlanner.java
	tajo-core/tajo-core-backend/src/main/java/org/apache/tajo/engine/planner/TargetListManager.java
	tajo-core/tajo-core-backend/src/main/java/org/apache/tajo/master/GlobalEngine.java
	tajo-core/tajo-core-backend/src/test/java/org/apache/tajo/engine/planner/TestLogicalOptimizer.java