Add localization for admin meta box

Hi, please change unit user-access-manager.php to better localization for non-english editors 🙂

//Admin meta boxes
            if (function_exists('add_meta_box')) {
                $aPostableTypes = $oUamAccessHandler->getPostableTypes();

                foreach ($aPostableTypes as $sPostableType) {
                    add_meta_box('uma_post_access', __('Access', 'user-access-manager'), array($oUserAccessManager, 'editPostContent'), $sPostableType, 'side');
                }

BTW: your plugin is Great! THX

https://ww.wp.xz.cn/plugins/user-access-manager/