* lamports->SOL in user-facing error msg
* Check for sufficient balance for spend and fee
* Add ALL option to solana transfer
* Rework TransferAmount to check for sign_only in parse
* Refactor TransferAmount & fee-check handling to be more general
* Add addl checks mechanism
* Move checks out of cli.rs
* Rename to SpendAmount to be more general & move
* Impl ALL/spend helpers for create-nonce-account
* Impl spend helpers for create-vote-account
* Impl ALL/spend helpers for create-stake-account
* Impl spend helpers for ping
* Impl ALL/spend helpers for pay
* Impl spend helpers for validator-info
* Remove unused fns
* Remove retry_get_balance
* Add a couple unit tests
* Rework send_util fn signatures