Add bash auto completion

This adds a basic bash auto-completion profile.

It supports 3 things at this time:
 - Auto-complete of container name (-n or -o)
 - Auto-complete of template name (-t)
 - Auto-complete of state names (-s)

It's configured in a way to be as little disruptive as possible, any
argument that's not explicitly handled by the profile will fallack to
bash's default completion.

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