Issue #1167 : Member Manager Fixes and implementation

* Implement the member research
 * Visual fix for the "add member" form
 * Use of the local storage to import all user (for the add member form)
 * Change the feedback of add and remove members
 * Add load state for the adding and removing users
 * Synchronize member number displays
 * Limit the number of members displayed

admin/group_list.php

@@ -386,6 +386,7 @@ $template->assign(
     'F_ADD_ACTION' => get_root_url().'admin.php?page=group_list',
     'U_HELP' => get_root_url().'admin/popuphelp.php?page=group_list',
     'PWG_TOKEN' => get_pwg_token(),
+    'CACHE_KEYS' => get_admin_client_cache_keys(array('groups', 'users')),
     )
   );