Better error handling in the ParserService

200b9eae019de50aa770c7fdf2daacb82c9080ce and
5cc3dfb83f6d2741be88a7f38e63f70dc6c63730 introduce some wonkiness.

 * Parse now acts on an error from TemplateRequest right away, instead of
   deferring till after Util.parse.

 * Message wasn't being properly stored in EnvError.

 * A restart flag is added to the errCB because only certain errors
   should invoked a process restart.

 * Removed fetching the default pageinfo when no pagename is supplied.

 * Redirect url is constructed from the prefix and target instead of
   req.path. Ex.

     /en/ -> /en/Main_page?oldid=12345
     /en/test -> /en/Test?oldid=34567

 * Cleans up favicon conditions now that they are supported.

 * html2wt() expects html param to be a string.

Change-Id: I2694f9f968a297f82294a54f1e1b2a75d66725eb