* fixed double handler of email activation link (wp_die doesn't stop the script for some reason);
* added redirects to login page with error notices instead of wp_die text;
* updated filters by status, avoid slow queries for getting users count;
* updated bulk-actions for changing statuses (moved to WP native dropdown)
* separate handlers for changing user statuses on wp-admin and frontend (partially implemented);
* created class UM()->common()->users() to handle user statuses in more clear format;
* deprecated old hooks and old functions