Show image used to spawn each container

Signed-off-by: Maxime Petazzoni <max@signalfuse.com>
Add missing field and reformat demo.yaml

Fixes #3.

Signed-off-by: Maxime Petazzoni <max@signalfuse.com>
Display ports in the fullstatus output

Signed-off-by: Maxime Petazzoni <max@signalfuse.com>