Improve admin LDAP user index

* Show which domain the current list is for
* Render text links as such

app/views/admin/ldap_users/index.html.erb

@@ -1,8 +1,13 @@
-<h2>LDAP users</h2>
+<h2>LDAP users: <%= @ou %></h2>
 
-<ul>
-  <li><%= link_to 'kosmos.org', admin_ldap_users_path %></li>
-  <li><%= link_to '5apps.com', admin_ldap_users_path(ou: '5apps.com') %></li>
+<h3 class="hidden">Domains</h3>
+<ul class="mb-10">
+  <li class="inline-block">
+    <%= link_to 'kosmos.org', admin_ldap_users_path, class: "ks-text-link" %>
+  </li>
+  <li class="inline-block ml-6">
+    <%= link_to '5apps.com', admin_ldap_users_path(ou: '5apps.com'), class: "ks-text-link" %>
+  </li>
 </ul>
 
 <table>