Provide the ability to update the license during the upgrade error screen

During the upgrade process, if the license is out of date the user is confronted with the attached error screen stating to check the logs. We also receive the following message in the log files.

2012-04-19 19:47:40,703 ERROR [main] [atlassian.confluence.upgrade.UpgradeLauncherServletContextListener] contextInitialized 1: 
  Cannot proceed with upgrade. Your current license does not entitle you to upgrade to this version of Confluence because it is now outside of its support period. 
  If you wish to renew it, please contact <a href="mailto:sales@atlassian.com">sales@atlassian.com</a>. If you have a new license, please enter it on this <a href="$CONTEXT/fixonly/fixlicense.action">page</a> and <b>restart</b>.

Considering that we know what is stopping the user, and provide the 'fixlicense.action' information in the logs we should provide this link (with a more specific message as well) in the error screen we show the user in the browser. Once a proper license is provided, the upgrade should continue as normal. This will make life easier for the user and also deflect 'failed upgrade' tickets from reaching the support queue.