added foreign key contraint for group and client in loan table

mifosng-db/migrations/core_db/V24__add-group-client-foreign-key-constraint-in-loan-table.sql

@@ -0,0 +1,7 @@
+ALTER TABLE m_loan
+ADD CONSTRAINT `fk_m_group_client_001`
+FOREIGN KEY (`group_id` , `client_id` )
+REFERENCES m_group_client (`group_id` , `client_id` )
+ON DELETE NO ACTION
+ON UPDATE NO ACTION
+, ADD INDEX `fk_m_group_client_001_idx` (`group_id` ASC, `client_id` ASC) ;