Remove unused BEAST_COMPILER_CHECKS_SOCKET_OVERRIDES.
Make beast::detail::chunk_encoded_buffers::to_hex() static
Use better base64 handling in ServerHandlerImp.
Make sure that handlers always return Json::objectValue.
First transaction
Create and use some testing API:

* Ledger::pointer
  createGenesisLedger(std::uint64_t start_amount_drops,
                      RippleAddress const& master);

* std::pair<RippleAddress, RippleAddress> createAccount();

* void
    makePayment(RippleAddress const& from, RippleAddress const& to,
                std::uint64_t amountDrops, Ledger::pointer const& ledger);
Add trust lines and currency payments.
Rename SerializedTransaction to STTx
[WIP] Advancing ledger.
[WIP] First ledger closed/advanced.