New Zero struct implements "compare with zero."
* Zero lets classes efficiently compare with 0, so
  you can use constructors like x < zero or y != zero.
* New BEAST_CONSTEXPR to handle Windows/C++11 differences
  regarding the constexpr specifier.
Updated example cfg for new validator public keys.

Signed-off-by: The Doctor <drwho@virtadpt.net>
Fix Visual Studio 2013 build
Enforce minimum version requirements on OpenSSL and Boost
Make is_set_bit a universal template function
Refactor usage of boost::format
Add beast::tagged_integer:
 * Wraps standard integer types to provide type-safety
 * Named types provide self-documenting semantics
 * Catches programmer errors involving mismatched types at compile time
 * Operators restrict mutation to only safe and meaningful operations
Add CleanCCPFiles.py, a utility for tidying up whitespace
Refactor ripple_overlay:
  * Use rvalue move to receive accepted sockets
  * Split asio dependent APIs to their own class and file
  * Update documentation
  * Organize code into different files
  * Make some members private
  * Rename things for clarity
Remove obsolete TODO files
Fix 64-bit Visual Studio build
Add [max_peers] doc to example cfg
Refactoring of container usage:
* New ripple container aliases use hardened_hash
* Use std::tuple instead of boost::tuple
* Use std unordered containers instead of boost
* Fix Destroyer for new containers
* Fix warning for fnv1a on 32-bit arch
* Validator fixes for new containers
Fix VS2013 warnings about integer conversions
Quality tests aren't manual
Split RPCHandler into a large number of small parts:
* Handler methods of RPCHandler are extracted into individual files.
* Helper methods of RPCHandler are converted into free functions, and
  extracted into individual files.
* Much code leaves ripple_app/rpc/RPCHandler.cpp and enters ripple_rpc/.
Fix display formatting of STAmount
Merge branch 'develop' of github.com:ripple/rippled into clean-cpp