Add metadata to JSON dump object

[3alpha]

Adding metadata to dump object could help with UX. Currently, only data that is needed to reconstruct devnet state is dumped to the JSON object. By adding metadata that is not used for reconstruction of state, namely hash and timestamp, UX could be improved because users would be able to:

• Identify block minted
• Inspect transactions made and further interact with devnet by using their hash
• Keep track of time manipulation

And finally, this would allow (somebody :) ) to build explorer on top of the devnet, which would be massive improvement in UX.

However, before this is done, few considerations should be made:

• Should this metadata be optional and controled via CLI flag?
• How to deal with backward compatibility? Adding metadata changes data structure dumped to JSON so custom deserializers would have to be written. There is no guarantee that dump works accross versions, however it would be nice that it does.