The RippleAddress class was used to represent a number of fundamentally
different types: account public keys, account secret keys, node public
keys, node secret keys, seeds and generators.
The class is replaced by the following types:
* PublicKey for account and node public keys
* SecretKey for account and node private keys
* Generator for generating secp256k1 accounts
* Seed for account, node and generator seeds
* A new, unified interface for generating random numbers and
filling buffers supporting any engine that fits the
UniformRandomNumberGenerator concept;
* Automatically seeded replacement for rand using the fast
xorshift+ PRNG engine;
* A CSPRNG engine that can be used with the new framework
when needing to to generate cryptographically secure
randomness.
* Unit test cleanups to work with new engine.