Mithril Client can restore Cardano Node from snapshot

[jpraynaud]

We need to implement a lightweight Mithril Client: (At this stage no certificate verification)

• Retrieve snapshots list from the Mithril Aggregator
• Retrieve a snapshot details from the Mithril Aggregator
• Download the archive of a snapshot (stored on a public server, http download only)
• Unpack the archive and restore it to a database folder of a Cardano node