Set new Melange version number to 0-5-20090913 in app.yaml.template.

Changed the conversion starter system to an update starter system. Also increased the usability of the update page by adding more information abou t each update that can be done and for which version number this applies.

Use the new optional argument to endRequest in the middleware Currently endRequest is called twice on an exception if Django intercepts the exception and returns it's own result. By setting optional=True we do not crash on 'assert self.in_request'.