gRPC support for account_tx and tx

- Add support for all transaction types and ledger object types to gRPC
  implementation of tx and account_tx.

- Create common handlers for tx and account_tx.

- Remove mutex and abort() from gRPC server. JobQueue is stopped before
  gRPC server, with all coroutines executed to completion, so no need for
  synchronization.

src/test/jtx/impl/last_ledger_sequence.cpp

@@ -0,0 +1,37 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2012, 2013 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include <test/jtx/last_ledger_sequence.h>
+#include <ripple/protocol/jss.h>
+
+namespace ripple {
+namespace test {
+namespace jtx {
+
+
+void
+last_ledger_seq::operator()(Env&, JTx& jt) const
+{
+    jt["LastLedgerSequence"] = num_;
+}
+
+} // jtx
+} // test
+} // ripple
+