Add pre/post hook for CRM_Mailing_BAO_MailingJob
This ticket is about adding pre, post hook to MailingJob and it involve:
- Call the pre/post hook inside
CRM_Mailing_BAO_MailingJob::deleteMailingJobto delete Mailing Jobs and add pre/post delete hook
- Replace all the DAO call with corresponding create and delete fn in the codebase.