Fix menus for relative pathing.

This fixes the Maven generated site so the paths are relative. This is
required so that multiple generations of the javadocs can be hosted at once,
and so no cross-linking occurs.

By: Luke GB <git@lukegb.com>

paper-api/src/site/site.xml

@@ -21,8 +21,8 @@
       <item name="Maven Repo" href="http://repo.bukkit.org/" />
     </menu>
     <menu name="API Documentation">
-      <item name="JavaDocs" href="http://jd.bukkit.org/apidocs/" />
-      <item name="Doxygen" href="http://jd.bukkit.org/doxygen/" />
+      <item name="JavaDocs" href="apidocs/" />
+      <item name="Doxygen" href="doxygen/" />
     </menu>
     <menu ref="reports" />
   </body>