import several fields for the handle update of service gateway

import fields for the update handle operation on service gateway

currently service gateway will cache some information from cc and need to be able to update these fields on ccng when they found that those fields are obsolete. the commit added gateway_data, gateway_name and credential for the 

put /v2/service_instance/:guid

api for the functionality.

tests done with the commit:
manually did the update operation on service gateway using v2 api and they can update the record in ccdb_ng.