add support for time.Time pointer in struct types

Allow to use pointer *time.Time as a type in combination with orm tags in struct. This enables to treat them as "empty" in JSON marshaling/unmarshaling when using 'json:"null,omitempty'.

orm/models_utils.go

@@ -137,6 +137,8 @@ func getFieldType(val reflect.Value) (ft int, err error) {
 		ft = TypeBooleanField
 	case reflect.TypeOf(new(string)):
 		ft = TypeCharField
+	case reflect.TypeOf(new(time.Time)):
+		ft = TypeDateTimeField
 	default:
 		elm := reflect.Indirect(val)
 		switch elm.Kind() {