TAJO-807: Implement Round(numeric, int) function. (Seungun Choe via hyunsik)
TAJO-494: Extend TajoClient to run a query with a plan context serialized as the JSON form. (jihoon)
TAJO-803: INSERT INTO without FROM throws ClassCastException. (Hyoungjun Kim via hyunsik)
TAJO-823: Missing INET4 handling in DatumFactory.cast(). (jihoon)
Almost completed window function plan.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-774

Conflicts:
	tajo-algebra/src/main/java/org/apache/tajo/algebra/Aggregation.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/CaseWhenPredicate.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/ColumnDefinition.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/CreateTable.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/DateValue.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/DropDatabase.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/DropTable.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/Expr.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/FunctionExpr.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/IsNullPredicate.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/LiteralValue.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/TimeValue.java
	tajo-algebra/src/main/java/org/apache/tajo/algebra/TimestampLiteral.java