Populate timestamp with the close time of the ledger when the snapshot was created

[JakeUrban]

What problem does your feature solve?

Some contracts depend on the ledger timestamp, and more specifically, expect the ledger timestamp to be continually increasing. Having the timestamp property in snapshot json files breaks this assumption.

What would you like to see?

Set the timestamp value to the most recent ledger close time from when the snapshot was created.

What alternatives are there?

Setting the timestamp manually after its created.