Refactor Overlay for Structured Network support:

* Move overlay up one directory
* Add abstract_protocol_handler, message_stream
* Add peer_protocol_detector
* Tidy up some declarations
* Use strand::running_in_this_thread instead of bool
* Update README.md
* Replace protocol message read loop:
  - Process data in arbitrary size chunks
  - message_stream extracts individual messages
  - peer_protocol_detector identifies the handshake
  - abstract_protocol_handler used for dispatching messages
* Remove unused protocol message types:
  - mtACCOUNT
  - mtCONTACT
  - mtERROR
  - mtGET_ACCOUNT
  - mtGET_CONTACTS
  - mtGET_VALIDATIONS
  - mtSEARCH_TRANSACTION
  - mtUNUSED_FIELD

Conflicts:
	src/ripple/module/app/main/Application.cpp
	src/ripple/module/app/misc/NetworkOPs.cpp
	src/ripple/module/app/peers/PeerSet.cpp

src/ripple/overlay/impl/Message.cpp

@@ -0,0 +1,95 @@
+//------------------------------------------------------------------------------
+/*
+    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 <ripple/overlay/Message.h>
+
+#include <cstdint>
+
+namespace ripple {
+
+Message::Message (::google::protobuf::Message const& message, int type)
+{
+    unsigned const messageBytes = message.ByteSize ();
+
+    assert (messageBytes != 0);
+
+    mBuffer.resize (kHeaderBytes + messageBytes);
+
+    encodeHeader (messageBytes, type);
+
+    if (messageBytes != 0)
+    {
+        message.SerializeToArray (&mBuffer [Message::kHeaderBytes], messageBytes);
+
+#ifdef BEAST_DEBUG
+        //Log::out() << "Message: type=" << type << ", datalen=" << msg_size;
+#endif
+    }
+}
+
+bool Message::operator== (Message const& other) const
+{
+    return mBuffer == other.mBuffer;
+}
+
+unsigned Message::getLength (std::vector <uint8_t> const& buf)
+{
+    unsigned result;
+
+    if (buf.size () >= Message::kHeaderBytes)
+    {
+        result = buf [0];
+        result <<= 8;
+        result |= buf [1];
+        result <<= 8;
+        result |= buf [2];
+        result <<= 8;
+        result |= buf [3];
+    }
+    else
+    {
+        result = 0;
+    }
+
+    return result;
+}
+
+int Message::getType (std::vector<uint8_t> const& buf)
+{
+    if (buf.size () < Message::kHeaderBytes)
+        return 0;
+
+    int ret = buf[4];
+    ret <<= 8;
+    ret |= buf[5];
+    return ret;
+}
+
+void Message::encodeHeader (unsigned size, int type)
+{
+    assert (mBuffer.size () >= Message::kHeaderBytes);
+    mBuffer[0] = static_cast<std::uint8_t> ((size >> 24) & 0xFF);
+    mBuffer[1] = static_cast<std::uint8_t> ((size >> 16) & 0xFF);
+    mBuffer[2] = static_cast<std::uint8_t> ((size >> 8) & 0xFF);
+    mBuffer[3] = static_cast<std::uint8_t> (size & 0xFF);
+    mBuffer[4] = static_cast<std::uint8_t> ((type >> 8) & 0xFF);
+    mBuffer[5] = static_cast<std::uint8_t> (type & 0xFF);
+}
+
+}