/**
  * Returns and/or create the single instance of this class.  
  *
  * @return  Charitable_General_Settings
  * @access  public
  * @since   1.2.0
  */
 public static function get_instance()
 {
     if (is_null(self::$instance)) {
         self::$instance = new Charitable_General_Settings();
     }
     return self::$instance;
 }
/**
 * Add dynamic settings groups.
 *
 * @see     Charitable_Gateway_Settings::add_gateway_settings_dynamic_groups()
 * @see     Charitable_Email_Settings::add_email_settings_dynamic_groups()
 * @see     Charitable_Email_Settings::add_licenses_group()
 */
add_filter('charitable_dynamic_groups', array(Charitable_Gateway_Settings::get_instance(), 'add_gateway_settings_dynamic_groups'));
add_filter('charitable_dynamic_groups', array(Charitable_Email_Settings::get_instance(), 'add_email_settings_dynamic_groups'));
add_filter('charitable_dynamic_groups', array(Charitable_Licenses_Settings::get_instance(), 'add_licenses_group'));
/**
 * Add settings to the General tab.
 *
 * @see     Charitable_General_Settings::add_general_fields()
 */
add_filter('charitable_settings_tab_fields_general', array(Charitable_General_Settings::get_instance(), 'add_general_fields'), 5);
/**
 * Add settings to the Payment Gateways tab.
 *
 * @see     Charitable_Gateway_Settings::add_gateway_fields()
 */
add_filter('charitable_settings_tab_fields_gateways', array(Charitable_Gateway_Settings::get_instance(), 'add_gateway_fields'), 5);
/**
 * Add settings to the Email tab.
 *
 * @see     Charitable_Email_Settings::add_email_fields()
 */
add_filter('charitable_settings_tab_fields_emails', array(Charitable_Email_Settings::get_instance(), 'add_email_fields'), 5);
/**
 * Add settings for the Licenses tab.
 *