code: function addActionIcon(action, ctrl) {
        ctrl.actionLabelNamesMap[action.name] = action.label;
        ctrl.actionIconNamesMap[action.name] = action.name;
        ctrl.actionIcons[action.name] = action.icon;
      }
docs: Registers an action's icon.
  Called internally by addAction().
  @param  {object} action  action object
  @param  {object} ctrl    instance of prmActionCtrl