Fixes for running in `mod_wsgi`. * No more `wsgiutil` for now, since it's easy enough to write the script. * Added a "context" to wiki parameters to communicate if we're running in normal mode, initialization mode (creating a new wiki), or background task mode. * Mercurial source-control uses this context to decide how to setup (or not) a command server. * Mercurial source-control is now sharing its command server per process, and tries to correctly shut it down on exit.