Fix usage of admin notices

[shadyvb]

Checking this add_action( 'all_admin_notices', array( __CLASS__, 'admin_notices' ) ); and seeing that the callback function admin_notices( $message, $is_error = true ) actually needs argument to display messages, makes the action registration pointless.

However, that same callback is used directly like in :

    public static function fail_php_version() {
        add_action( 'plugins_loaded', array( __CLASS__, 'i18n' ) );
        self::notice( __( 'Stream requires PHP version 5.3+, plugin is currently NOT ACTIVE.', 'stream' ) );
    }

defined here

    public static function notice( $message, $is_error = true ) {
        if ( defined( 'WP_CLI' ) ) {
            $message = strip_tags( $message );
            if ( $is_error ) {
                WP_CLI::warning( $message );
            } else {
                WP_CLI::success( $message );
            }
        } else {
            self::admin_notices( $message, $is_error );
        }
    }

I recall there was some logic to retain messages locally in the class and then outputting in via the callback registered to that action. Anyway, we need to fix that.