Universal Port: Simplified administration for rippled servers

This implements part of the "Universal Port" feature. It allows peer, RPC over http, RPC over HTTPS, Websocket, and Secure Websockets to be served on a single listening port. In this version, websockets is disabled and only legacy peer connections are allowed to become peers. Peer HTTP upgrade requests are given a "503 Service Unavailable" with a JSON content body with a handful of IP addresses to visit.
Reviewers: @ximinez, @JoelKatz 
It appears there is a bug in Boost 1.55, which may or may not only show in VS 2013 Update 3, but the `flat_map` with a pointer as key *breaks the build* in my environment.

https://svn.boost.org/trac/boost/ticket/9332

If the solution is to upgrade to Boost 1.56, then we need to update relevant documentation, etc.