message: Add selectedItem property into radiogroup question
diff: @@ -2,6 +2,7 @@ import { Serializer } from "./jsonobject";
  import { QuestionFactory } from "./questionfactory";
  import { QuestionCheckboxBase } from "./question_baseselect";
  import { surveyLocalization } from "./surveyStrings";
  +import { ItemValue } from "./itemvalue";
  /**
  * A Model for a radiogroup question.
  @@ -16,6 +17,10 @@ export class QuestionRadiogroupModel extends QuestionCheckboxBase {
  protected getFirstInputElementId(): string {
  return this.inputId + "_0";
  }
  + public get selectedItem(): ItemValue {
  + if (this.isEmpty()) return null;
  + return ItemValue.getItemByValue(this.visibleChoices, this.value);
  + }
  /**
  * Show "clear button" flag.
  */
  