This MR allows a node to export and import chains snapshots.
- Context export/import is added through the
- The snapshot feature is implemented in
- Finally, new node command is added.
This MR depends on !1067 (merged) and must be merge after.
More info can be found in this post: https://blog.nomadic-labs.com/introducing-snapshots-and-history-modes-for-the-tezos-node.html