Don't use MultiSocket in Overlay:
The MultiSocket is obsolete technology which is superceded by a more
straightforward, template based implementation that is compatible with
boost::asio::coroutines. This removes support for the unused PROXY handshake
feature. After this change a large number of classes and source files may be
removed.
Add [overlay] configuration section (experimental):
This configuration section uses the new BasicConfig interface that supports
key-value pairs in the section. Some exposition is added to the example cfg
file. The new settings for overlay are related to the Hub and Spoke feature
which is currently in development. Production servers should not set
these configuration options, they are clearly marked experimental in the
example cfg file.

Conflicts:
	src/ripple/overlay/impl/OverlayImpl.cpp
	src/ripple/overlay/impl/OverlayImpl.h
	src/ripple/overlay/impl/PeerImp.cpp
	src/ripple/overlay/impl/PeerImp.h
Set version to 0.26.4-rc1
Revert "Add [overlay] configuration section (experimental):"

This reverts commit 856fd9d69f9b5d114982d9de361bcdf5ecbba505.
Set version to 0.26.2-rc2
Add [overlay] configuration section (experimental):
This configuration section uses the new BasicConfig interface that supports
key-value pairs in the section. Some exposition is added to the example cfg
file. The new settings for overlay are related to the Hub and Spoke feature
which is currently in development. Production servers should not set
these configuration options, they are clearly marked experimental in the
example cfg file.
Always detect ssl in HTTP server
Add new Handler interfaces
Persist HTTP peer io_service::work lifetime
Add HTTP::Writer interface:
The Writer interface allows clients to supply a "pull" style object to provide
responses to HTTP Requests. The interface is designed to support a coroutine
based implementation.
Tidy up includes
Split implementation into three headers
Use ssl_bundle in SSLPeer
Call HTTP Handler with legacy peer handshake
Use ssl_bundle in Overlay::Peer
Construct Overlay::Peer with ssl_bundle and legacy handshake
Pass legacy peer handshakes through Overlay
De-pimpl HTTP::Server
Add Section::name:
The Section object now stores its name for better diagnostic messages.
Add doors section in cfg