code: function(type) {
      var ctl = { type: type };
      var idx = this.form.controls.length;
      var id = this.form.signature + ':' + idx;
      ctl.id = 'c-' + utils.sha256(id).substring(0, 8);
      this.form.controls.push(ctl);
      return ctl;
    }
docs: Creates a control of specified `type`.
  
  The id for each control is a hash based on `this.form.controls.length`.
  Two subsequent calls will yield the same result, if no controls
  were placed into `this.form.controls` in between.
  
  @private
  @param type {String} One of `checkboxGroup`, `radioGroup`, `inputText`, `selectMenu`.