allow subtypes to put extra content in main.jelly

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@17879 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/resources/hudson/model/Computer/index.jelly

@@ -83,6 +83,7 @@ THE SOFTWARE.
         </j:otherwise>
       </j:choose>
 
+      <st:include page="main.jelly" optional="true"/>
     </l:main-panel>
   </l:layout>
 </j:jelly>
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