Add inferno, a distributed cross-platform hosted OS

Adds the [Inferno OS](http://inferno-os.org/). An `inferno` command is added to start inferno with a copy of Inferno's runtime setup correctly for the user in `$XDG_DATA_HOME/inferno`. The command line shell can be used or the windowing runtime executed with `wm/wm wm/login -u username`.