Transformer support for oc-system module as per sonic-net/SONiC#1790

Author: Verma-Anukul

config/transformer/models_list

@@ -11,3 +11,9 @@ openconfig-if-aggregate.yang
 openconfig-interfaces-annot.yang
 openconfig-mclag.yang
 openconfig-mclag-annot.yang
+openconfig-system.yang
+openconfig-system-annot.yang
+openconfig-system-terminal.yang
+openconfig-messages.yang
+openconfig-system-logging.yang
+openconfig-aaa.yang