Cleanup unit test support code (RIPD-1380):

* Remove `src/test/support/mao`
* Flatten `src/test/support/jtx` to `src/test/jtx`

src/test/jtx/impl/jtx_json.cpp

@@ -0,0 +1,56 @@
+//------------------------------------------------------------------------------
+/*
+    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 <BeastConfig.h>
+#include <test/jtx/jtx_json.h>
+#include <test/jtx/utility.h>
+#include <ripple/json/json_reader.h>
+#include <ripple/basics/contract.h>
+
+namespace ripple {
+namespace test {
+namespace jtx {
+
+json::json(std::string const& s)
+{
+    if (! Json::Reader().parse(s, jv_))
+        Throw<parse_error> ("bad json");
+
+}
+
+json::json (char const* s)
+    : json(std::string(s)){}
+
+json::json (Json::Value jv)
+    : jv_ (std::move (jv))
+{
+}
+
+void
+json::operator()(Env&, JTx& jt) const
+{
+    auto& jv = jt.jv;
+    for (auto iter = jv_.begin();
+            iter != jv_.end(); ++iter)
+        jv[iter.key().asString()] = *iter;
+}
+
+} // jtx
+} // test
+} // ripple