* add json, which does the thing with json, move print to Rust's {:?}
* add --head NUM, to limit how much work gets done for print, json, verify
* add verify-internal, which very carefully checks ledger format without
trying first to "recover" it
* exit with errors on mis-usage
All CLI apps that use clap (in other words, except for bench-streamer)
can use crate_version! to take the version from Cargo.toml.
This change addresses #700.
* add recover_ledger() to deal with expected common ledger corruptions
* add verify_ledger() for future use cases (ledger-tool)
* increase ledger testing
* allow replicate stage to run without a ledger
* ledger-tool to output valid json
Rob Walker
Kazuyoshi Kato
Michael Vines