code: function removeActionIcon(action, ctrl) {
        delete ctrl.actionLabelNamesMap[action.name];
        delete ctrl.actionIconNamesMap[action.name];
        delete ctrl.actionIcons[action.name];
      }
docs: Deregisters an action's icon.
  Called internally by removeAction().
  @param  {object} action  action object
  @param  {object} ctrl    instance of prmActionCtrl