Add various ways of launching a browser for HelpInfo links, add support for
changing the prefix for those links and better formatting of them, cleanup
comments.

Patch by: jat
Review by: rjrjr


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@6691 8db76d5a-ed1c-0410-87a9-c151d255dfc7