BIP39 support for ED25519

[jasny]

Support BIP39 for generating private keys. For ED25519, BIP39 should an alternative to the current (brainwallet) seeding method.

Choosing BIP39 seeding should result in the same key pair for seed when using Ledger.

The current keyPairFromSeed method should move to a separate class BrainwalletEd25519. And a new class Bip39Ed25519 should be added.

To test if the implementation is correct

• Generate a new wallet for LTO Network on Ledger
• Get the 24-word seed
• Use the seed to generate an Ed25519 keypair using Seasalt
• Convert the public key to an address using the python or java library.
• The address should be the same address as shown on the Ledger device.

[jasny]

This is not supported in clients of other languages (js, python). BIP32 / BIP39 is only supported for secp256k1. No need to support this unless it's changed in the LTO protocol and supported everywhere.