TAJO-699: Create a table using LIKE. (Prafulla T via hyunsik)

Closes #21
TAJO-851: Timestamp type test of TestSQLExpression::testCastFromTable fails in jenkins CI test. (Hyoungjun Kim via hyunsik)

Closes #23
TAJO-842: NULL handling in JDBC. (Hyoungjun Kim via jinho)

Closes #18
TAJO-842: NULL handling in JDBC. (fixed a missing log in CHANGES)
TAJO-846: Clean up the task history in woker. (jinho)

Closes #20
TAJO-266-new