listing sort improvement

[celogeek]

The list of snapshot seems ordered by date.

Is it possible to be able to group them:

• by host
• by owner (if implemented later)
• by label

Then display the snapshot in the reverse order of the date is very useful.

• date (reverse)

So this way, for each host and label, we have the list of snapshot in reverse order.

And the option --last, should take in account those groups.
For now --last 1 return only the latest snap across all host and label. It would be more useful to have the latest snap for each host and label.

This could be a parameter, like --group host,label --last 1