* SDK: Refactor (read|write)_keypair
Split file opening and data writing operations
Drop filename == "-" stdio signal. It is an app-level feature
* keygen: Move all non-key printing to stderr
* keygen: Adapt to SDK refactor
* keygen: Factor keypair output out to a helper function
* Add mnenomic keypair generation and recovery to cli
* Use password input to retrieve mnemonic phrase
* Direct users without keypair file to use solana-keygen
* Add signature to blob
* Change Signable trait to support returning references to signable data
* Add signing to broadcast
* Verify signatures in window_service
* Add testing for signatures to erasure
* Add RPC for getting current slot, consume RPC call in test_repairman_catchup for more deterministic results
* Migrate from ring to ed25519-dalek
* Move gen_keypair_file test to a more appropriate location
* Fixup bench-exchange and add helper fn for single deterministic keypair
* Update golden