Add snapshots tab

[imobachgs]

Adds a list of snapshots using dummy data. It is just a PoC because there is not much data to show regarding a snapshot yet. Finally, the actions at each row are:

• "Rollback" is the snapshot is not the default one;
• "Reboot" is the snapshot is the default one but it is not active.

There are many things to improve, like indicating which is the default snapshot, improving the date/time format, etc. And, of course, displaying real data.

[lslezak]

Looks good! :+1:

[lslezak]

Let's merge the current work.