Update snapshot links to new documentation.

Author: eldering

website/about.shtml

@@ -61,7 +61,7 @@ If you are using (an adapted version of) DOMjudge, we would be glad to hear abou
 </ul>
 
 <p>For a detailed list of all software please refer to the
-<a href="snapshot/admin-manual/admin-manual-2.html#install_config:requirements">
+<a href="snapshot/manual/overview.html#requirements-and-contest-planning">
 administrator manual</a>.</p>
 
 <h2>Authors and contact</h2>

website/development.shtml

@@ -86,7 +86,7 @@ at your own risk.</p>
 
 <p>Additional information can be found in the administrator's manual,
 especially the
-<a href="/snapshot/admin-manual/admin-manual-11.html">appendix with developer information</a>.</p>
+<a href="/snapshot/manual/develop.html">appendix with developer information</a>.</p>
 
 <p>If you have any questions left, don't hesitate to ask at the <a href="https://www.domjudge.org/mailman/listinfo/domjudge-devel">DOMjudge-devel mailinglist</a>.</p>