* gnu/system/shadow.scm (%base-user-accounts): New variable.
* gnu/system.scm (<operating-system>)[users]: Use it as the default value.
* gnu/system/examples/bare-bones.tmpl (users): Use it.
* gnu/system/examples/desktop.tmpl (users): Likewise.
* doc/guix.texi (operating-system Reference, User Accounts): Adjust
accordingly.
* gnu/system/examples/bare-bones.tmpl: Change 'packages' and
'host-name'. Remove D-Bus, Avahi, and SLiM services, and add lsh
instead.
* gnu/system/examples/desktop.tmpl: New file.
* Makefile.am (EXAMPLES): Add it.