i18n-ified the admin/staff users templates.

htdocs/theme/default/templates/admin/usermanagement/adminusers.tpl

 {include file="header.tpl"}
 
-<h2>AdminUsers</h2>
+<h2>{str tag="adminusers" section="admin"}</h2>
+
+<p>{str tag="adminusersdescription" section="admin"}</p>
 
 {$adminusersform}
 

htdocs/theme/default/templates/admin/usermanagement/staffusers.tpl

 {include file="header.tpl"}
 
-<h2>StaffUsers</h2>
+<h2>{str tag="staffusers" section="admin"}</h2>
+
+<p>{str tag="staffusersdescription" section="admin"}</p>
 
 {$staffusersform}