Add DDL script code to create table SCHEDULER_JOBS, SCHEDULER_JOB_CHAINS and SCHEDULER_JOB_CHAIN_NODES script

The scheduler.sql script for Oracle, Postgres, MSSQL Server, Sybase and DB2 is missing the DDL command to create the table SCHEDULER_JOBS, SCHEDULER_JOB_CHAINS and SCHEDULER_JOB_CHIAN_NODES.

This behavior has been observed as stated in https://sourceforge.net/p/jobscheduler/discussion/486121/thread/a7a9bd22