Rewrite lxc-ls in python

Rewrite lxc-ls in python

This rewrite is mostly compatible with the shell version.
--active and -1 still work and behave as they used to.

This adds --running, --stopped and --frozen as state filters.

A new "fancy" view is also implemented (can be used with --fancy) and
will show containers in a column-based interface with the following fields:
 - name
 - state
 - ipv4
 - ipv6
 - pid of init

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>