Authorize access to admin panel, etc.

Adds a separate admin namespace and base controller, with authorization
by looking up the admin property in the user's LDAP account.

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

@@ -0,0 +1,4 @@
+<h2>Admin Panel</h2>
+<p>
+  Ohai there, admin human.
+</p>

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

@@ -1,8 +1,8 @@
 <h2>LDAP users</h2>
 
 <ul>
-  <li><%= link_to 'kosmos.org', ldap_users_path %></li>
-  <li><%= link_to '5apps.com', ldap_users_path(ou: '5apps.com') %></li>
+  <li><%= link_to 'kosmos.org', admin_ldap_users_path %></li>
+  <li><%= link_to '5apps.com', admin_ldap_users_path(ou: '5apps.com') %></li>
 </ul>
 
 <table>

app/views/shared/status_forbidden.html.erb

@@ -0,0 +1,2 @@
+<h2>Access forbidden</h2>
+<p>Not with those shoes, buddy.</p>