admin-dashboard-columns.php

<?php
/**
 * Plugin Name: Admin Dashboard Columns
 * Description: Reactivates the option to set the number of admin dashboard columns
 * Version: 1.0.0
 * Author: Bernhard Kau
 * Author URI: https://kau-boys.de
 * License: GPLv3
 * License URI: http://www.gnu.org/licenses/gpl-3.0
 */

/*
This is a solution posted on WordPress Stackexchange by @ocean90 as a plugin
http://wordpress.stackexchange.com/questions/126301/wordpress-3-8-dashboard-1-column-screen-options/126307#126307
*/

function wpse126301_dashboard_columns() {
    add_screen_option(
        'layout_columns',
        array(
            'max'     => 4,
            'default' => 1
        )
    );
}
add_action( 'admin_head-index.php', 'wpse126301_dashboard_columns' );