Simplify RipplePublicKey
Remove unused and obsolete Ripple identifiers and tidy up:

These identifiers were part of a failed set of classes to replace
the functionality combined into RippleAddress. They are not used
and therefore can be removed.

* Remove RippleAccountPrivateKey
* Remove RippleAccountPublicKey
* Remove RippleAccountID
* Remove RipplePrivateKey
* Remove RipplePublicKeyHash
* Remove RippleLedgerHash
* Remove unused withCheck argument
* Remove CryptoIdentifier
* Remove IdentifierStorage
* Remove IdentifierType
* Add missing include