implement a simple public_key call for the keychain (no hd wallets yet)

[vladiuz1]

the public_key must be returned in one of these formats:

• hex
• base64
• base58
• wif (with optional params: --prefix, --compression, --version from this page.)

For wif (wallet import format) you shall use the following default option values:

--prefix      = ''
--version     = 0x80
--compression = 0x01

--hd option will return a hierachical deterministic public key derived from either saved public key [un]encrypted private key.

Another option to implement is --derive. This will return a public key derived from private key rather than returning the saved public key from wallet storage (derived during the creation of the key pair).

If this option is selected and the private key is encrypted such request will prompt user for password.

Once hierarchical deterministic wallets are ready, the --derive option will similarly derive the public key directly from private key rather than from saved public key in the wallet storage.

• hex format
• base64 format
• wif format according to http://learnmeabitcoin.com/glossary/wif
• --compression option for wif format
• --version option for wif format
• --prefix option for wif format
• --hd option
• --derive option

[roman-modelist-dev]

Is it necessary to implement base64 and wif format, considering that we abandoned from the wif format in the array-core?
Also what about hd and derive options? Are these options related to this issue?