support create and drop function statement like apache hive

[ambition119]

jira links https://issues.apache.org/jira/browse/CALCITE-2663

Flink uses the calcite SQL engine. CREATE FUNCTION statement Can help create SQL functions and user-defined functions, like apache hive . Create function statemen:

CREATE [OR REPLACE] FUNCTION [IF NOT EXISTS] [db_name.]function_name AS class_name
  [USING JAR|FILE|ARCHIVE 'file_uri' [, JAR|FILE|ARCHIVE 'file_uri'] ];

DROP FUNCTION [IF EXISTS] function_name;

sample sql demo:

CREATE TABLE emp (
 id int,
 name varchar,
 birthday timestamp,
 other_info varchar
)

CREATE FUNCTION
    Date_Format AS 'org.apache.udf.DateFormat'
USING JAR 'file:/udf/udf-0.0.1-SNAPSHOT.jar';

CREATE FUNCTION
    Get_Json_Object AS 'org.apache.udf.GetJsonObject'
USING JAR 'file:/udf/udf-0.0.1-SNAPSHOT.jar';

SELECT
  count(id) as total_emp,
  Date_Format(birthday,'yyyy') as `year`,
  Get_Json_Object(Get_Json_Object(other_info,'address'),'province') as province
FROM emp
WHERE
  Date_Format(birthday,'yyyy') = '1990'
AND  
  Get_Json_Object(GetJsonObject(other_info,'address'),'province')
GROUP BY 
  `year`,
  province
;