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/InnerObjectFormats.h

@@ -0,0 +1,47 @@
+//------------------------------------------------------------------------------
+/*
+    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.
+*/
+//==============================================================================
+
+#ifndef RIPPLE_PROTOCOL_INNER_OBJECT_FORMATS_H_INCLUDED
+#define RIPPLE_PROTOCOL_INNER_OBJECT_FORMATS_H_INCLUDED
+
+#include <ripple/protocol/KnownFormats.h>
+
+namespace ripple {
+
+/** Manages the list of known inner object formats.
+*/
+class InnerObjectFormats : public KnownFormats <int>
+{
+private:
+    void addCommonFields (Item& item);
+
+public:
+    /** Create the object.
+        This will load the object will all the known inner object formats.
+    */
+    InnerObjectFormats ();
+
+    static InnerObjectFormats const& getInstance ();
+
+    SOTemplate const* findSOTemplateBySField (SField const& sField) const;
+};
+
+} // ripple
+
+#endif