Remove from given app or plugin the disabled field.

@param {String} apporplugin The plugin/app name
as it's typed by the user.
function (apporplugin) {
    if (config.plugins[apporplugin] !== undefined) {
      config.plugins[apporplugin].disabled = undefined;
      configHelpers.saveConfig();
    } else if (config.apps[apporplugin] !== undefined) {
      config.apps[apporplugin].disabled = undefined;
      configHelpers.saveConfig();
    } else {
      throw new Error(
        'Cannot enable, given app or plugin ' +
        apporplugin +
        ' is not configured.');
    }
  }