improving the error handling. Error page shouldn't be 200.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@9874 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/resources/hudson/util/HudsonFailedToLoad/index.jelly

+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form" xmlns:i="jelly:fmt">
+  <l:layout>
+    <l:header title="Hudson" />
+    <l:side-panel />
+    <l:main-panel>
+      <h1><img src="${imagesURL}/48x48/error.gif" alt="[!]"/><st:nbsp/>${%Error}</h1>
+      <pre>${it.stackTrace}</pre>
+    </l:main-panel>
+  </l:layout>
+</j:jelly>
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