message: add FormatPropertyProvider.delete
diff: @@ -40,6 +40,7 @@ interface FormatPropertyProvider<T> {
  isApplicable(model: Model): boolean
  get(model: Model): T | undefined
  set(model: Model, value: T): void
  + delete(model: Model): void
  }
  namespace FormatPropertyProvider {
  @@ -66,6 +67,9 @@ namespace FormatPropertyProvider {
  },
  set(model: Model, value: T) {
  model._staticPropertyData[name] = value;
  + },
  + delete(model: Model) {
  + delete model._staticPropertyData[name];
  }
  };
  }
  