* Add helper to get a protobuf cell without bothering with bincode
* Add conversion back to EntrySummaries
* Add LedgerStorage::get_block_entries
* Add ledger-tool bigtable entries subcommand
* Move CliEntries into ledger_tool::output for now
* Fetch entries with read-only token
Introduce a struct to store all of the relevant slot/root information, and then output all in one go at the end as either human-readable or json. There are some slight changes to the human-readable format for the case of an empty ledger