* Code added for calculating an account's generating balance. (CIYAM AT support yet to be added).
* Added associated code in Block for calculating next block's timestamp, generating balance, base target, etc.
* ValidationResult enum added to Block, mostly to aid debugging.
* Block.isValid() now returns ValidationResult instead of boolean.
* Block.isValid() now has added proof-of-stake tests.
* Some blockchain-related constants, like feature release heights/timestamps, moved from Block to BlockChain.
* Added better Block constructor for use when creating a new block.
* Added helpful 'navigation' methods to Block to get to block's parent (or child).
* Changed visibility of block's individual signature calculators to protected, in favour of public sign() method.
* Added asset existence check to Payment.isValid.
* All current transaction objects (qora.transaction.*) now have private subclassed transaction variable to save multiple casts in various methods.
* Also added to above:
* isInvolved(Account) : boolean
* getRecipients() : List<Account>
* getAmount(Account) : BigDecimal
* Added BlockRepository.getLastBlock() to fetch highest block in blockchain.
* Added diagnostics to HSQLDBRepository.close() to alert if there are any uncommitted changes during closure.
(Currently under suspicion due to possible HSQLDB bug!)
* Old "TransactionTests" renamed to "SerializationTests" as that's what they really are.
* New "TransactionTests" added to test processing of transactions. (Currently only a PaymentTransaction).
* PaymentTransformer.toBytes() detects and skips null signature. This was causing issues with Transaction.toBytesLessSignature().
Needs rolling out to other transaction types if acceptable.
