SignerListSet txn and InnerObjectFormats (RIPD-182):

Add support for the SignerListSet transaction as a step toward
multi-sign support.

As part of the SignerListSet implementation, add InnerObjectFormat
templates (similar to TxFormats and LedgerFormats) and enforce them
in STObject, STArray, and STParsedJSON.

src/ripple/protocol/impl/InnerObjectFormats.cpp

@@ -0,0 +1,55 @@
+//------------------------------------------------------------------------------
+/*
+    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 <ripple/protocol/InnerObjectFormats.h>
+
+namespace ripple {
+
+InnerObjectFormats::InnerObjectFormats ()
+{
+    add (sfSignerEntry.getJsonName ().c_str (), sfSignerEntry.getCode ())
+        << SOElement (sfAccount,              SOE_REQUIRED)
+        << SOElement (sfSignerWeight,         SOE_REQUIRED)
+        ;
+}
+
+void InnerObjectFormats::addCommonFields (Item& item)
+{
+}
+
+InnerObjectFormats const&
+InnerObjectFormats::getInstance ()
+{
+    static InnerObjectFormats instance;
+    return instance;
+}
+
+SOTemplate const*
+InnerObjectFormats::findSOTemplateBySField (SField const& sField) const
+{
+    SOTemplate const* ret = nullptr;
+    auto itemPtr = findByType (sField.getCode ());
+    if (itemPtr)
+        ret = &(itemPtr->elements);
+
+    return ret;
+}
+
+} // ripple