- Add document describing virtual clusters
  - Non-root clusters are not yet described, will be done in another
    patch
- Change title of design document to avoid confusion

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Bernardo Dal Seno <bdalseno@google.com>

The biggest change is going from a command line parameter for specifying
a daemon's directory to using an environment variable. Some other things
are clarified.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>

I am currently able to run a 2-node virtual cluster on my machine,
with a very ad-hoc setup. But the results show clearly that this is
doable, and that given the right tools, setting up such a cluster will
be quite easy.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>